• by Mark Walsh  @markfwal, November 15, 2010

As anticipated, Facebook on Monday unveiled a new e-mail service, but as part of a broader platform that creates a hub for all online communication including SMS, chat, and email and a "social inbox" that automatically prioritizes messages from Facebook friends. Users can also see all the online coversations they have had with friends.

At a press conference in San Francisco today, Facebook CEO Mark Zuckerberg said the company wanted to provide a modern messaging system that was simple and easy to use, combining email with more informal communication tools like SMS and instant messaging.

Yes, Facebook users will be able to get an @Facebook.com email address as part of the initiative, but Zuckerberg stressed that email was only "one part of it." But with 500 million members worldwide, Facebook's new email system instantly becomes a serious threat to the likes of Gmail and Yahoo Mail. Of those half billion users, 350 million use Facebook's existing message service to send 4 billion messages a day, according to Zuckerberg.

Until now, the social network has offered a basic internal messaging tool and online chat, but not a competing email offering. The platform is built around three main components:

Seamless messaging: People can get messages in their inbox from SMS, chat, email or Facebook's existing message service in one central location via mobile devices as well as the desktop Web.

Conversation history: All messages with someone will be archived together in one place, whether sent over chat, email or SMS. The idea is to see everything you've discussed with each friend as a single conversation.

Social Inbox: Because Facebook already knows who users' friends are, it can filter messages based on their social graph. So the inbox will only contain messages from your friends and their friends--all other messages will go into an "Other" folder for separate review. "One result of this is a social inbox where the signal-to-noise ratio is high," said Zuckerberg.

The new messaging system will be rolled out over the next few months, beginning with a small group of invitation-only users. Zuckerberg explained that advertising will work in email as it does elsewhere on Facebook. "There's a space on the right with some ads and we try to make them as relevant as possible," he said, adding that ads would not be targeted based on the content of messages.

But Charlene Li, founder of digital strategy consulting firm Altimeter Group, pointed out in a blog post that the unified messaging system will give even more data to track. While the company currently has no plans to monetize that information, "privacy advocates are standing at the ready to understand how that data will be used," she wrote in a blog post today.

With the volume of messaging already taking place on Facebook, advertising through the expanded communication system could become a significant new revenue stream for the company. A new report from comScore last week showed that Facebook already accounts for a quarter of online display ads viewed in the U.S.

Facebook's push into email poses a new problem for Google and Yahoo, the dominant players in the space, which already run text and display ads with their respective email offerings. For his part, Zuckerberg scoffed at press reports last week referring to Facebook's expected email launch as a potential "Gmail killer."

"I think they have a great product," he said of Google and Gmail. "Email is still really important to a lot of people, but we just think this simpler kind of messaging is going to be how a lot more people sift a lot of their communication." Leading that trend are younger users in their teens and twenties who shun email in favor of options like SMS and IM.

With the launch of email, one question is whether Facebook will continue to block Google from gaining access to its users' contacts data. The two Web giants have been engaged in a very public fight since Google stopped allowing Facebook users to import contacts from Gmail because of Facebook's lack of reciprocation.

Meanwhile, other competitors are already upgrading their email services to become more diverse. Yahoo late month launched the latest (beta) version of its 303 million-user email service, touting Facebook and Twitter integration, the ability to view photos and videos right from the inbox and faster email search.

And AOL on Sunday began testing a new message service that will aggregate messages from a users' multiple email accounts in one place. Like Facebook's new offering, new features are also intended to make it a central hub for online communication generally, not just email.

But Altimeter's Li maintains that Facebook has an advantage over rivals in its filtering system tied to the social graph. "By centering communications on friends -- rather than features and a simple email address -- Facebook is creating a special kind of lock-in unavailable to other portals, your friends," she wrote.