darth_ender said:

You know, your Facebook friends automatically notify you every time they update their status or something. But friends here are...just friends. What's the point? Nevertheless, I've got some of you on my friend list, but just because I don't doesn't mean I don't like you. Don't feel left out that the coolest forum member hasn't yet added you. Just friend me and I'll friend you back! Unless I don't like you.

It might simply serve as a quick way to send a PM to someone with whom you frequently speak.