The site's roughly 500 million users send over four billion IMs and Facebook messages everyday (though only about 350 million actively use the Facebook messaging platform).
These numbers make it clear that part of Facebook's future relies on it's relevancy as a communications platform, and thus the launch of the code-named Project Titan.
Though Facebook users will eventually be able to get a Facebook.com e-mail address, Mark Zuckerberg and Facebook engineer Andrew Bosworth were careful to explain that this is not yet another e-mail client. Instead, it's a rethinking of the Facebook messaging system and a new take on digital communication. It attempts to integrate e-mail, IM and SMS into one ongoing conversation.
At the heart of the new Facebook messaging platform is what the company has called "seamless messaging," a system that blurs the conventional lines between methods of communication. Users who prefer to communicate via e-mail can still do so, but, if you're logged into Facebook with Chat open, an incoming e-mail will pop up in an IM window, so that you can quickly read it. Your quick response will automatically be sent back as an e-mail. If you step away from your PC, and your friend continues the conversation, the message will then get pushed to your phone via the Facebook iPhone app (presumably coming to Android in the future).
Instead of e-mail threads and separate chat logs, all communication via Facebook is dumped into a single conversation history. To try and limit the noise, Facebook is leveraging what it knows about you and your network of friends to separate important messages from those that aren't immediately registered as spam by Gmail's Priority Inbox.
The early hype of "Gmail killer" seems to be slightly off base, but the tight integration that breaks down walls between communication methods should set off alarms at Google. Eventually, when Facebook launches IMAP e-mail integration, the new service will work with Gmail. According to Zuckerberg, the new Facebook Messages system will be rolled out very slowly over the next couple of months, starting today with an invite-only beta launch!