Hey Facebook fans, rumour has it you may be getting email addresses ending with "@facebook.com" as early as Monday. It's a thought that likely has privacy advocates cringing as even more user data would fall under the control of the world's largest social network.

The rumoured service wouldn't be just an updated version of Facebook's currently pathetic Inbox, either, but an actual webmail client to compete with services such as Gmail and Hotmail, according to TechCrunch. Codenamed Project Titan, the new email service is expected to be announced Monday at a special Facebook press event during the Web 2.0 Summit in San Francisco.

Rumours of a Facebook email service first surfaced in February. At the time, it was suggested that your Facebook vanity URL might be automatically assigned to you as your @facebook.com email address.

Adding credence to TechCrunch's report are two features in Facebook's press invitation suggesting Monday's event is all about messaging. The invite features Facebook's Inbox/Messages icon used in its mobile phone applications. The invite also features a red and blue border similar to an airmail envelope.

Of course, an email inbox isn't the only possibility for a messaging-themed Facebook event (assuming the decorations on the invitation are actually hints). On Wednesday, GigaOm theorised that multiuser group chat will soon be integrated into Facebook's smartphone applications. The technology blog didn't mention Monday's event as a possible launch date, only guessing multiuser chat will launch "within months."

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If Facebook Webmail is coming, it will likely be welcomed by a large number of Facebook users. But a Facebook email service is almost certain to cause concern among privacy advocates. Using Facebook for mail would put even more of your data in the hands of the social network. And the company would almost certainly mine your messages for keywords to better target advertising at you, similar to what Google's Gmail does now.

There may also be concern that Facebook would control, and possibly block, email messages flowing through its servers. In early 2009, torrent site The Pirate Bay introduced a new feature that let Facebook users send each other links to torrent files through Facebook's Inbox messaging service. It didn't take long before Facebook started blocking private messages containing torrent links, according to Wired.

At the time, Facebook argued it had the right to block this content since the company forbids its members to use the service for unlawful purposes such as disseminating copyrighted material. Facebook can also be overly aggressive with its anti-spam filtering, which could hamper use of a Facebook email service if you start sending too many email messages at once.

If Facebook does launch a webmail service, it will certainly be good timing. Market research firm Gartner recently predicted that "20 percent of workers will use social networks as their primary vehicle for business communications by 2014." Facebook email would fit into that scenario perfectly.