In a remarkable coincidence today, I read this post, an interview with an anonymous Facebook employee (the post’s authenticity is being highly debated on the web), which contains this excerpt:
How do you think we know who your best friends are? But that’s public knowledge; we’ve explicitly stated that we record that. If you look in your type-ahead search, and you press “A,” or just one letter, a list of your best friends shows up. It’s no longer organized alphabetically, but by the person you interact with most, your “best friends,” or at least those whom we have concluded you are best friends with.
And then on Facebook, I was messing around with my settings and I noticed this when I clicked the ‘edit options’ link:
So it’s true. I just think that’s quite an amazing thing – I almost didn’t believe it. And for the record, no, I’m not paranoid about privacy issues for the simple reason that I don’t have hundreds of photos on Facebook, though I am very much for privacy as a right.
One Size Fits One 
is that the recommended friends link that gives it away?i read that article but ddnt find the feature on fb! and one of the comments on the article said they couldnt find it either..
Hey – no I don’t think it’s the recommended friends link. I have no idea how they determine it, probably by tracking whose pages you visit? I’m sure FB have all that info among the vast amount of user data they collect daily.