Eliminating 3rd-party devs was only half the issue, the other half was the lack of velocity.

I've been saying for a while now that my cofounder and I add more functionality to our startup every two weeks than Twitter's 4,000 employees add to theirs in an entire year. Now this is obviously an apples-and-oranges comparison for all sorts of reasons, yet all caveats aside I think it's still pretty telling.