Sharing something about yourself most people in a room don't know is an ice-breaker that is fairly common in seminars, training classes and team building exercises - where strangers are put together and need to complete some sort of task or engage in conversation.
This request usually comes after you've separated into smaller groups to complete some task - although occasionally it's something the whole group does if it's not too many people.
Most people say something fairly innocuous and self-congratulating. I was staying at a Hotel in Florida and wrestled an alligator into submission that was threatening guests around the pool - or something in that vein. What people decide to share may be funny, touching, sad, or really surprising - to the point where you may ask yourself what sort of context filter they have on sharing personal information with strangers. As a student of the human condition I find that any time I've participated in one of these exercises it's always pretty interesting.
You'll find some interesting answers to this type of question in online forums. One problem with these, same as for any online activity, is that there is no context - you can't see what the person looks like, hear their tone or observe their body language. So their message loses something. Saying "I love the Jonas Brothers", or "I used to be quite a party girl" would be unusual if I said it but for someone else you'd think - sure, now tell me something I don't know.
The whole idea of sharing something most people don't know reminds me of the way I used to go to confession when I was a young practicing Catholic. I'd give the priest a taste of what I'd been up to in general terms - stealing, lying, using the Lord's name in vain etc. etc. etc. but never any details. I was lying while confessing my many sins, but I never mentioned that to Father Kelley because I was an altar boy after all. I guess I could have told him I stole a beer out of the basement of the church during summer bible camp and drank it with my friend Tim during lunch when I was 8 years old - but that's probably too much detail.