A snapshot server, now upgraded to 1.8, has been running fine since 1.8 launch. But after creating a automated Pumpkin farm underground, after a few hours logged out and returned, a 16x16 chunk reverted to original state.
Everything in that chunk all the way to bedrock is as originally generated.

Console code:
08.09 21:39:27 [Server] Server thread/INFO Minecrafter1981 left the game
08.09 21:39:27 [Disconnect] User Minecrafter1981 has disconnected, reason: TextComponent{text='Disconnected', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
08.09 21:38:47 [Multicraft] Minecrafter1981 ran command Message of the Day
08.09 21:38:47 [Server] Server thread/INFO Minecrafter1981 joined the game
08.09 21:38:47 [Connect] User Minecrafter1981, IP 2.110.90.112
08.09 21:38:47 [Server] User Authenticator #2/INFO UUID of player Minecrafter1981 is c069fcac-15f9-4645-8c37-1350cdf7d97b
08.09 21:29:00 [Server] Server thread/INFO Minecrafter1981 left the game
08.09 21:29:00 [Disconnect] User Minecrafter1981 has disconnected, reason: TextComponent{text='Disconnected', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
08.09 21:25:00 [Multicraft] Minecrafter1981 ran command Message of the Day
08.09 21:25:00 [Server] Server thread/INFO Minecrafter1981 joined the game
08.09 21:25:00 [Connect] User Minecrafter1981, IP 2.110.90.112
08.09 21:25:00 [Server] User Authenticator #1/INFO UUID of player Minecrafter1981 is c069fcac-15f9-4645-8c37-1350cdf7d97b
08.09 21:23:43 [Server] Server thread/WARN Can't keep up! Did the system time change, or is the server overloaded? Running 2039ms behind, skipping 40 tick(s)
08.09 21:23:39 [Server] Startup Done (2.610s)! For help, type "help" or "?"
08.09 21:23:39 [Server] Server thread/INFO Preparing spawn area: 71%
08.09 21:23:38 [Server] Server thread/INFO Preparing spawn area: 10%
08.09 21:23:37 [Server] Server thread/INFO Preparing start region for level 0
08.09 21:23:37 [Server] Server thread/INFO Preparing level "Testing"
08.09 21:23:37 [Server] Server thread/INFO Starting Minecraft server on 185.28.188.128:27043
08.09 21:23:36 [Server] Server thread/INFO Generating keypair
08.09 21:23:36 [Server] Server thread/INFO Default game type: SURVIVAL
08.09 21:23:36 [Server] Server thread/INFO Loading properties
08.09 21:23:36 [Server] Server thread/INFO Starting minecraft server version 1.8
08.09 21:23:33 [Multicraft] Server already running
08.09 21:23:33 [Multicraft] Received start command
08.09 21:23:29 [Multicraft] Loaded config for "Vanilla Minecraft 1.7.9"
08.09 21:23:29 [Multicraft] Starting server!
08.09 21:23:29 [Multicraft] Loading server properties
08.09 21:23:29 [Multicraft] Received start command
08.09 21:12:15 [Multicraft] Not restarting crashed server.
08.09 21:12:15 [Multicraft] Server stopped
08.09 21:12:15 [Multicraft] Looks like a crash, check the server console. Return value: 1
08.09 21:12:15 [Multicraft] Server shut down
08.09 21:12:05 [Server] Server Watchdog/ERROR This crash report has been saved to: /./crash-reports/crash-2014-09-08_21.12.04-server.txt
08.09 21:12:03 [Server] Server Watchdog/FATAL Considering it to be crashed, server will forcibly shutdown.
08.09 21:12:03 [Server] Server Watchdog/FATAL A single server tick took 60.00 seconds (should be max 0.05)
08.09 21:10:37 [Server] Server thread/WARN Can't keep up! Did the system time change, or is the server overloaded? Running 3188ms behind, skipping 63 tick(s)
08.09 21:10:33 [Server] Startup Done (23.800s)! For help, type "help" or "?"
08.09 21:10:33 [Server] Server thread/INFO Preparing spawn area: 96%
08.09 21:10:32 [Server] Server thread/INFO Preparing spawn area: 78%
08.09 21:10:31 [Server] Server thread/INFO Preparing spawn area: 73%
08.09 21:10:31 [Server] Server thread/INFO Preparing spawn area: 70%
08.09 21:10:29 [Server] Server thread/INFO Preparing spawn area: 63%
08.09 21:10:27 [Server] Server thread/INFO Preparing spawn area: 55%
08.09 21:10:27 [Server] Server thread/INFO Preparing spawn area: 51%
08.09 21:10:25 [Server] INFO ... 12 more
08.09 21:10:25 [Server] INFO at fn.a(SourceFile:380) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at fn.a(SourceFile:45) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at fn.b(SourceFile:373) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at java.io.DataInputStream.readUTF(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:25 [Server] INFO at java.io.DataInputStream.readUTF(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:25 [Server] INFO at java.io.DataInputStream.readFully(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:25 [Server] INFO at java.io.BufferedInputStream.read(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:25 [Server] INFO at java.io.BufferedInputStream.read1(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:25 [Server] INFO at java.io.BufferedInputStream.fill(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:25 [Server] INFO at java.util.zip.InflaterInputStream.read(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:25 [Server] INFO at java.util.zip.InflaterInputStream.fill(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:25 [Server] INFO Caused by: java.io.EOFException: Unexpected end of ZLIB input stream
08.09 21:10:25 [Server] INFO at java.lang.Thread.run(Unknown Source) [?:1.7.0_55]
08.09 21:10:25 [Server] INFO at net.minecraft.server.MinecraftServer.run(SourceFile:417) [minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at po.i(SourceFile:210) [minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at net.minecraft.server.MinecraftServer.a(SourceFile:286) [minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at net.minecraft.server.MinecraftServer.k(SourceFile:315) [minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at qs.c(SourceFile:81) [minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at qs.e(SourceFile:129) [minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at bfy.a(SourceFile:77) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at fz.a(SourceFile:67) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at fz.a(SourceFile:71) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at fz.a(SourceFile:106) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at fn.a(SourceFile:48) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO at fn.a(SourceFile:386) ~[minecraft_server.jar:?]
08.09 21:10:25 [Server] INFO u: Loading NBT data
08.09 21:10:25 [Server] Server thread/ERROR Couldn't load chunk
08.09 21:10:25 [Server] Server thread/INFO Preparing spawn area: 44%
08.09 21:10:23 [Server] Server thread/INFO Preparing spawn area: 35%
08.09 21:10:23 [Server] Server thread/INFO Preparing spawn area: 29%
08.09 21:10:21 [Server] Server thread/INFO Preparing spawn area: 21%
08.09 21:10:21 [Server] Server thread/INFO Preparing spawn area: 18%
08.09 21:10:18 [Server] Server thread/INFO Preparing spawn area: 10%
08.09 21:10:17 [Server] Server thread/INFO Preparing spawn area: 5%
08.09 21:10:17 [Server] Server thread/INFO Preparing spawn area: 0%
08.09 21:10:11 [Server] Server thread/INFO Preparing start region for level 0
08.09 21:10:11 [Server] INFO at java.lang.Thread.run(Unknown Source)
08.09 21:10:11 [Server] INFO at net.minecraft.server.MinecraftServer.run(SourceFile:417)
08.09 21:10:11 [Server] INFO at po.i(SourceFile:210)
08.09 21:10:11 [Server] INFO at net.minecraft.server.MinecraftServer.a(SourceFile:235)
08.09 21:10:11 [Server] INFO at bqm.d(SourceFile:85)
08.09 21:10:11 [Server] INFO at fz.a(SourceFile:13)
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.<init>(Unknown Source)
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.<init>(Unknown Source)
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.readHeader(Unknown Source)
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.readUShort(Unknown Source)
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.readUByte(Unknown Source)
08.09 21:10:11 [Server] INFO java.io.EOFException
08.09 21:10:11 [Server] INFO at java.lang.Thread.run(Unknown Source) [?:1.7.0_55]
08.09 21:10:11 [Server] INFO at net.minecraft.server.MinecraftServer.run(SourceFile:417) [minecraft_server.jar:?]
08.09 21:10:11 [Server] INFO at po.i(SourceFile:210) [minecraft_server.jar:?]
08.09 21:10:11 [Server] INFO at net.minecraft.server.MinecraftServer.a(SourceFile:225) [minecraft_server.jar:?]
08.09 21:10:11 [Server] INFO at net.minecraft.server.MinecraftServer.a(SourceFile:183) [minecraft_server.jar:?]
08.09 21:10:11 [Server] INFO at bqj.b(SourceFile:94) [minecraft_server.jar:?]
08.09 21:10:11 [Server] INFO at bqn.c(SourceFile:62) [minecraft_server.jar:?]
08.09 21:10:11 [Server] INFO at fz.a(SourceFile:13) ~[minecraft_server.jar:?]
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.<init>(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.readHeader(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.readUShort(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:11 [Server] INFO at java.util.zip.GZIPInputStream.readUByte(Unknown Source) ~[?:1.7.0_55]
08.09 21:10:11 [Server] INFO java.io.EOFException
08.09 21:10:11 [Server] Server thread/ERROR Exception reading ./Testing/level.dat
08.09 21:10:11 [Server] Server thread/INFO Preparing level "Testing"
08.09 21:10:07 [Server] Server thread/INFO Starting Minecraft server on 185.28.188.128:27043
08.09 21:10:06 [Server] Server thread/INFO Generating keypair
08.09 21:10:06 [Server] Server thread/INFO Default game type: SURVIVAL
08.09 21:10:06 [Server] Server thread/INFO Loading properties
08.09 21:10:06 [Server] Server thread/INFO Starting minecraft server version 1.8
08.09 21:09:24 [Multicraft] Loaded config for "Vanilla Minecraft 1.7.9"
08.09 21:09:24 [Multicraft] pid file contains pid 15088
08.09 21:09:24 [Multicraft] Starting server!
08.09 21:09:24 [Multicraft] Loading server properties
08.09 21:09:21 [Multicraft] Loading server properties