I have two.

The first one involved [site that I won't name to not influence others], an online web cam site. My friends and I in middle school would go on the sight for pure fun sometimes. We would just talk to random people for a laugh. Until one guy we met, who had asked for our bra sizes. This particular day a new friend came over with a few of my other friends. She took off her shirt and told him. Then, we all (shirts still on) told him. The next day a screenshot of the chat and a picture of my friends and me was faxed to my grandparents. To this day I have no idea how it happened, but I suspect my creepy cousin was on the other side of the camera, because his family and mine were on the outs. My cousin was on that site religiously...

The second time (chronologically the first), I was in elementary school. I hung out with my older sister and her friends. They were all three years older so I wanted to be them, of course. I would do anything to impress them. This one friend of hers came over and I knew she was a troubled-kid. Later on in the night, she dialed a sex operator line. You basically picked who you wanted to talk to and chose a description of the person. I remember clear as day her talking to a man in a raspy voice and telling him we had all just gotten out of a steam shower and were licking ice cream. Fast forward to a few nights ago... My sisters and I are having dinner with my mother and we're all talking about the bad things we did as children. Low and behold my sister brings up the sex line! (Something I expected we would BOTH take to the grave!) I was mortified even though I'm older now, because my mother mentioned her man friend who worked on the sex line!!!

Lesson learned: don't give into peer pressure. Don't do something that you know you shouldn't be doing...