I wouldn't be particularly happy to wander into a random Payless Shoe store to find a hoarde of 100 zombies on top of me (unable to run away). Unless the person setting the trap goes through a considerable amount of risk and cost to set this up.
Also, in terms of game realism, think of the amount of resources that would be necessary to attract a large number of zombies into a place without being injured, then contain them without being injured.
I would only be doing it if the trap would trigger in my general location, to kill hostile survivors in my area.
I'm not shooting the idea down, I just don't think that you should be able to mail your zombies away to another location far-far-away. This kind of trap would, and should, spring locally.
(Which I recognize sucks for those of you not near lots of other players.)