This article at CNet takes a detailed look at the growth of social gaming through Apple's iPhone, a market many developers — and Apple themselves — are still struggling to figure out. The piece also speculates on how such games and networks will continue to evolve
"While competition has spawned better features among these services, the future brings a growing need for a more unified network. Even if all these networks begin to become impossible to differentiate, users are eventually going to want a less-disjointed platform when jumping from game to game, and app to app. Thus far Facebook, and even Twitter to some degree have provided that constant, just by giving users a way to log in to these platforms. The unification can shake out in a number of ways though, the most likely of which is consolidation. Open Feint can continue to grow until it's snatched up by a larger company (like Apple). Or it can begin absorbing, or muscling out the other, less popular networks. As mentioned before, Apple plays a big part in this: not only in how it changes the hardware, but also how it continues to evolve the business of the App Store and information sharing between applications."