Nick Bradbury makes a good point about the longevity of operating system APIs compared to the more brittle APIs of the web:
You might think you’re immune to this problem if you only integrate with APIs created by large players such as Twitter, Facebook and Google. But in recent years we’ve seen Twitter switch to a new authentication system, Facebook deprecate FBML, and Google discontinue several APIs. All of these changes have broken, or will break, existing apps.