This is the risk you run when building on top of other companies. Generally speaking, it's always more favorable to BE that platform, rather than be building on top of it. We've seen this over and over in the Twitter development community. Zynga is the rare case on Facebook where they are generating so much money for Facebook they have enough leverage against Facebook to level the playing field somewhat. 99% of other platform developers/startups do not have this luxury and can be wiped out at the whim of the platform.