It seems like most of these social gaming companies are taking steps towards having games be less reliant on Facebook as a platform. Zynga is developing their own games site and HeyZap seems to be creating a pipeline of sorts b/w publishers and games.

yet facebook seems to be the center of the social internet. people don't leave facebook (i'm talking about your average fb user). the value proposition would have to be pretty high to get these people to move to another site to play games

Right because using the Facebook platform to gain tens of millions of users and hundreds of millions in revenue off simplistic games with poor graphics has definitely been a poor business decision.

if your a gaming company thats made millions thus far on fb, and VC's have backed you on the assumption that you would continue to make millions, and facebook decides they want to get into the lucrative social-gaming market & begins pushing their own brand of games and making it a little bit harder for users to find your games, what do you do as a company?

i just don't think it's a sustainable long-term strategy

Right it is the all eggs in one basket advise that everyone gets. You business plan should incorporate branching off of Facebook / iPhone / whatever closed ecosystem and into others so that if one closes your are not at the mercy of that single revenue stream. There is nothing wrong with bootstrapping on or developing for a closed ecosystem (financially)(and I don't get into the politics), but one should really have a plan to diversify ones self from a single revenue channel.