Network effects are still horrible barriers to overcome on social networks or phone platforms. Once a company has large numbers of active users they tend to win, and once they start winning they have little incentive to care about the well being of individual third party developers. Once they have the eyeballs the third party developers want access to, they can treat most of them like dirt, and they can still count on more lining up to use their API.

If a company like Google struggles to launch a new social network with their existing huge user base, you know its hard. Yes social networks and platforms do die, like MySpace and RIMM, and new ones burst in to prominence like Pinterest or Android, but for every new network or platform that succeeds, hundreds or more probably thousands fail.

Small third party developers have strong incentives to put up with the risks involved in using API's provided by dangerous companies like Twitter, Facebook and Apple because they have to if they want to get access to all the users those companies own.