I did some extra testing. It seems like it behaves like this if you're nearby spawner trying to spawn a copy of the item with the same nbt properties every tick. I only did the later testing in Mincraft 1.4.5, but I would guess this is the behavior in snapshot 12w49a too.
Axel Wickman
I did some extra testing. It seems like it behaves like this if you're nearby spawner trying to spawn a copy of the item with the same nbt properties every tick. I only did the later testing in Mincraft 1.4.5, but I would guess this is the behavior in snapshot 12w49a too.