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Try it. Start a comment in Facebook, type the "@" symbol, and when you type the first letter of a friend or group's name, a drop-down menu appears and creates an easily navigated link to that friend or group's page. When you mention and link to somebody like this, it notifies that person that you've done so.
There's more coolness: According to Inside Facebook, "Admins can 'use Facebook as a Page' and publish comments that mention themselves on the posts of other Pages in order to attract people to their Page."
In other words, this is a way to get around Facebook's spam filter that often won't let you include URLs in comments (hey, that's just like Mashable), letting you slip in a link to your page that might actually stick.