What determines what 9 friends show up on your Facebook timeline?

[Leila.]

Alright, so I was just on my facebook, and I was just curious as to how the 9 friends on the little Friends module on your timeline are chosen. I know Facebook might say they choose them at random, but I find it a little hard to believe, because usually it's people I'm pretty good friends with, and lots of times, they show up a lot.

However, there is one right now that is there who is a good friend of mine, but we don't really interact at all on Facebook, besides me sometimes embarrassingly creeping on him/crushing (awkward). So, why are some really good friends there and then him and a couple of others I barely talk to?
Is it because they last looked at my stuff too?

Just curious! Thanks!