Up and Down-facing dispensers don't spawn spawn eggs correctly.

Up and Down-facing dispencers spawn mobs inside the dispencer block, whereas side-facing dispencers spawn the mobs to the adjacent block. Spawning mobs inside the block can cause them to suffocate and get killed.

Heres a video demonstrating the bug:
http://www.youtube.com/watch?v=ymfFVPisLG4