http://www.facebook.com/notes/facebook-engineering/the-underlying-technology-of-messages/454991608919 http://www.facebook.com/notes/facebook-engineering/the-und

http://www.facebook.com/notes/facebook-engineering/the-underlying-technology-of-messages/454991608919 http://www.facebook.com/notes/facebook-engineering/the-under... talks a bit more about this decision.