I was extremely anti-Facebook for the first two years that it was in operation. I think my attitude was based primarily on the fact that I was a grad student (often working as a TA) and all the undergrads I taught were obsessed with it, and used it to hook up and stalk their exes, etc.
I finally gave it a chance last summer, though (after trying in vain to make new friends in Iceland)... and I can easily say that is has revolutionized my social life here abroad. I don't think I would have had as much use for it while I was still in the US, but it has been fantastic for meeting new people in Iceland... now I'm a proselytizer and have gotten 99% of my friends to join, which has been a lot of fun.
I also really like the ease of sharing pictures via Facebook albums... so much easier than sending out mass e-mails with photo attachments, or even using a blog. It's definitely one of my top 3 visited websites every day (including TFP).
