Facebook is probably using an algorithm that picks from among the friends that the user has interacted the most with. At least that's what I would do if I were implementing it. They already use such an algorithm internally to detect if your account is compromised (i.e., if the set of friends with whom you communicate changes sharply at some point.)

Given that Facebook might be doing this, it is likely that the top few friends would be of the opposite gender, in a heteronormative context. This intuitive expectation has been confirmed in research studies of social networks. e.g., http://www.cs.cmu.edu/~jure/pubs/msn-www08.pdf ("people tend to converse more frequently and with longer durations with the opposite gender").

Perhaps pc can confirm/refute whether this is true in his case?

I just did some testing by refreshing the "http://www.facebook.com/deactivate.php page and I always got two same friends. Next I realized that it was displaying a picture where both of us were tagged. I had untagged myself from a bunch of other albums, so the other 3 friends picked were pretty much random.

So, its definitely giving high priority if you both are tagged in the same picture irrespective of the fact if you are really good friends with them or not. One of the friend tagged in a pic with me was added about 4-5 months ago, whereas my other friend I have know her since 2001, but on facebook since 2004/2005. 70% of my friends added are from the 2004 - 2007 time period.

And "cucina" is a feminine noun, right?