I think the numbers started at 100000.
Prior to that, elementary school, I used PowWow and Mplayer to socialize with pretty much only Californians.. since everyone on the internet back then lived in CA. That was a weird time. I of course was 18 for.. oh, 10 years.
I believe I've met 2-3 people with lower numbers than mine.
edit: Wow, just signed in, been awhile. None of my friends online and the web app doesn't tell you their last time online. Not sure if the desktop apps still do.