I finally joined. It is rare that someone has a fresh feel for this network, so let me share what it feels like to be web-initiated, but a FB rookie.
First, Facebook is not merely big, it is teeming with activity. The sheer volume of data pumped through your homepage is amazing. It's like having a 2 second conversation with everyone you've known since grade school every single day. As someone who blogs and gchats regularly, I found the internet to be the equivalent of a close-in suburb - busy, but not unmanageable. I realize now that the metaphor is incorrect. I was at a cafe wondering where everyone was. Yesterday, I walked into the bar next door and found a crush of people partying like it was the end of the world.
Second, FB is extremely voyeuristic. It is a giant game of "I'll show you mine if you show me yours." I'll post photos of me, sure - but I get the guilty pleasure of poring over your tales of vactions gone wrong, long nights at the bar, trips to places I've never been, weddings, boyfriends, announcements of sexual leanings. It's like being a gossip columnist at a large high school, snooping, getting tips, rumor-mongering, and engaging in endless stupid games. (Poking, I'm looking at you).