I checked on FAQs on facebook for `Which friends appear in the left column of my profile?` and it said:
"The left column of your profile may display two types of friend lists:
a changing selection of friends always appears under the "Friends" heading in the left column of your profile.
The selection includes many friends who you publicly interact with the most.
Examples of public interactions include Wall posts,
comments and mutually attended events —
Facebook will never show friends based on whose profiles you choose to view or who you interact with over messages and chat.
Feature specific friends or groups
In addition to your general list of friends,
you can choose to feature specific friends (e.g.,
roommates or coworkers)
or groups to which you belong.
Learn how to do this here.
Hope this helps...
though I still don`t know if I believe it because I have some people come up who I don`t speak to much compared to others...??
But this is the most definite answer I can find.