Every type of map lasts for a while then dies off. Look @ golem maps. I used to like them then they got boring. Now you hardly ever see golem games on battle.net. Same goes for mass games (mainly because they're boring).
Anyway bounds are starting to get unoriginal, and it really pisses me off when the bound name has nothing to do with the bound. For example I was playing a bound called 'Nautical Bound'. The only thing in the entire bound that related to the ocean/sea was that your zerglings were called sea men (not intended to be nasty).
Most of the obstacle ideas are used up, so each bound is a combination of the obstacles in a different order with each of them being slightly different. I think what battle.net needs is a completely new type of game. Something that doesn't have anything to do with:
Bounds
RPGs
The Normal Game
Any type of massing game
Defense games
Movies
ect...
Obviously if I knew about a new game type I would post it, but I don't.
Ironicially after the above, I do like bounds.