The reason that isn't too much of a problem is that if an app is only available on one store, a significant fraction of people will simply not install it. Businesses don't want to lose customers like that, but the mere fact that they could will force Monopoly App Store to act more reasonably.

We'll probably see 3-4 major stores that manage to get enough mindshare for people to actually install them, and a lot of apps available on a 2-ish-store subset of them.