I think Facebook has eliminated a lot of things that the reunions used to provide. I already knew, for the most part, what everyone looked like and what they were doing now - kind of took away the surprise.
Despite the Facebook phenomenon, there's no way to escape THE conversation: "Hey, great to see you... so what are you doing now? Oh yeah, I'm (fill in the blank). Are you married? Kids? (Awkward pause as conversation hits inevitable and merciful end...). Okay, well... I'm going to grab a drink/go to the bathroom/catch up with (Blank). Talk to you soon!"
You wear your life on your face. There was one guy who continues to mountain bike, workout, ride his cruiser to work... and frankly, he hasn't aged at all. One of my high school crushes? Still working in the bar and smoking, 20 years later - and looks like she's ten years older than the rest of us. Just one more reason that I can't understand why more people don't put activity and exercise at the top of their list of priorities, along with friends and family and before work.
There is never a good time to admit you are a personal trainer, unless you want to face a barrage of questions or comments wherein the other person is either seeking validation for their excuses, or absolution for their choices. I refused to give either. Kept the earlier aforementioned conversations considerably shorter than they had to be.
Finally, what's most surprising about the reunion - is how the cliches and stereotypes turn out to be 100% true, despite your hoping otherwise.