The interesting problem, though, is who exactly do I know? Assuming I know a person, do I really want to be friends on Facebook?
Unless you are a salesman, politician, or entertainer, the value of Facebook diminishes as you get too many friends. After all, being friends entails getting (in some cases) multiple updates on the daily details of their life. Do I really need to now that the dude I hung out with for a few weeks back in 1998 is sick today? Or even worse, that he is doing great on some trivia quiz?
So this all creates some difficult decisions when I get a friend request. One of the hardest decisions concerns people that I know now or sort of know now. This category of person is somebody that I actually see on a regular basis for whatever reason. By adding him as a friend today, it almost seems that I'm committing to following his daily updates for the rest of my life. Perhaps the standard procedure will be to quietly drop the friendship after not being in regular contact for a few years. On the other hand, it may still be good to have some sort of link to that kind of person going forward, especially if we are in the same profession or have a lot of mutual friends.
Another dilemma is what to do with the person you sort of knew years ago. Yes, we went to school together years ago. But we were not even really friends then. Is there a sufficient basis to be "friends" now for the first time just based on the common experience and perhaps mutual friends? In this situation, it at least helps if the friend request has a message to go with it. Otherwise, it is this almost creepy agreement to open myself up to your voyeurism (photos, updates, contact information) in exchange for the same -- looking at each other through a double blind window (if such a thing exists).
I should disclaim that although some of the friend requests have been close calls both ways (both accept and reject), and I've been fairly limited with respect to the people that I'll allow into my Facebook life. I'm happy with the friends that I have (and there are still many real life friends who I hope will join Facebook). It will be interesting to see how it all shakes out in the years and decades to come, and what my reaction will be to finding out that the dude I met at a conference in 2002 reached a new level in the Nickelback trivia game.