Possible Duplicate:
Facebook Api - send private messages to friends
I know that it is not officially possible to send private messages through FB API. Every thread in SO says so too. But I was using RockMelt browser and when you invite somebody, a private message is sent to them. Means it is possible to send private messages through API. More importantly, Facebook is okay with it.
Any guesses on how they are using it? Is it some HTTP POST trick using sockets? BTW, we are going to use this feature only on user initiated actions.