Facebook wants you to stop using Gmail and check your email with them. Look out for Project Titan.
Like we have been saying for a while. Facebook does not want you to EVER leave their site. They want you to play your games there, leave your pictures there, and now read and write your email there as well. This is just the beginning in a whole series of moves to become THE place where people will go to do anything online. Supposedly inside Facebook they call it the "Gmail killer." As others have observed, Facebook already has the largest repository of pictures, games, calendar events and upcoming local shopping deals. It makes perfect sense for them to install a full blown email client. The announcement is coming this Monday. We will keep you updated.