not how it works for me! i have friends on fb that i haven't talked to or seen since high school. i don't use fb proper but it's good to know that it remembers everyone so i don't have to. i guess it goes the other around as well.
There is something wrong with this for me.. If you don't remember people, are they really worth kepeing around ?
It is a great way to reach someone you want to get in touch with after a really long time, but that scenario is far more rare than people claim when they speak of the 'magic of facebook'.
How in the world are you ever going to know if you never contact them again?