Several good points about Twitter’s success that all web service developers should pay attention to. Especially this one, which is applicable to any web 2.0 site:
Twitter even lets competitors (like FriendFeed or Facebook) slurp its content into their services. But instead of strengthening them, it seems to strengthen Twitter. It’s the new version of embrace and extend: inject and take over. […]
There’s a real lesson to Facebook here about giving other services (like Twitter) access to their social graph. They have the best one going, but because they try to keep users coming back to their interface, and even the applications built on their service have to live in Facebook, they end up as a ghetto rather than a true internet service. It’s the data, not the interface! Let other people use your data, build on it, and it will still belong to you. Hold it too tight, and they will compete with it.
With just a little catch — Twitter has no business model whereas Facebook is kinda sorta not very far from being profitable if they wanted to, if I remember correctly.