I check facebook daily to see what's up in the news feed and browse around a bit. I use facebook as a link to connect with people I thought I'd never see.. I can't believe I've been able to know and say hi to high school and elementary school classmates that I hadn't seen in years. A couple of them go as far as my kindergarten class!
I know a couple of my friends recently saw each other during Easter break after going their separate ways after high school which I found to be very cool. I don't think it would've been possible if they didn't find each other on facebook.
The profiles (depending on how much each person puts in there) is exciting to see to know where people are and what they're doing. If it wasn't for facebook, I wouldn't of known a couple of my high school friends are fathers and a couple others are either engaged or married.
Forums are more for people of the same interest to discuss topics relating to each other. Since Geoexpat is one for expats in HK, it's only suiting to have a variety of sub-forums discussing various topics relating to HK. And since we're all located in HK anyways with it's convenient public transit system, it's only suiting we're able to meet up for stuff more often. 