When using a command block with the command set to...

summon Wolf ~ ~2 ~ {CustomName: "@p" , Owner: "@p" }

...the summoned wolf will have the name @p instead of the actual player name and belongs to the non-existing player with the name @p.

When using the new selector JSON format for texts introduced in the latest snapshot, e.g. like...

summon Wolf ~ ~2 ~ {CustomName: {selector: "@p"} , Owner: {selector: "@p"} }

...the wolf does not have any name.