I am making a fireball cannon with command blocks using

/summon Fireball ~ ~ ~1 {direction:[0.0,0.0,1.0]}

I noticed that the summoned fireball slows down.
According to http://minecraft.gamepedia.com/Entity#Motion_of_entities fireballs use to have a drag of 0, but if you summon one with the direction tag it has some drag.

How to reproduce:
1. execute /summon Fireball ~ ~ ~1

2. look at the fireball, it slows down. There is drag
3. punch fireball
4. it doesn't slowdown. There is no drag