According to Techcrunch’s sources, a full webmail client integrated with The One and Only Social Network will debut next Monday. This is why it may become your favorite webmail service.

If I were Google, Yahoo or Hotmail, I’d be very nervous. Facebook Mail could be a killer not only because of its potential instant size, but because of its natural advantage at making mail more useful.

That’s the important thing for Facebook users and everyone else. This may become the only 100% useful mail service out there, only showing you the emails you are actually interested in. To me, if they have the right user interface, that’s enough reason to switch from Gmail.

Why use Facebook for email?

Facebook has 500 million active users. Gmail is estimated at 170 million registered users, while Yahoo has 303 million and Hotmail is still king of the hill at 364 million. Of course, not every Facebook boy and girl will jump on its mail bandwagon, but chances are that a huge percentage of you will. In fact, it’s not a crazy assumption that almost everyone will, even if that means having yet another mail account added to your computer, phone or tablet.

The fact is that it may be just too convenient to ignore. Facebook users are already used to its internal messaging system. For many, this will be a nice upgrade that will let them add these messages to their mail boxes. Remember that Facebook’s mail is rumored to have external mail client access as well as its dedicated webmail interface. It will be easy to have it in every single gadget you own.

But, most importantly, Facebook’s users would probably jump in because the social nature of Facebook fits perfectly with the social nature of mail. The irony here is that their mail system could be a raging success because of what many people criticize: Facebook tracks all your moves.