If the rumors are correct, this might explain why Facebook and Google have been recently with concerns to user data--Google has been preventing Facebook from importing Gmail data, and perhaps this is because such a feature would help people migrate from Gmail to Facebook email with ease.

Is Google right to be worried? We won't know for sure until Monday, but, in the meantime, here are five ways Facebook email could keep Gmail on its toes:

Photo Slideshows

Gmail is still behind when it comes to photo integration--sending users to external Websites to view albums in Picasa or Flickr. Even if Facebook ignores these services in email, it will still have its own (immensely popular) photo service to rely on. A slideshow viewer directly in Facebook email, like , could be a killer feature.

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