A few times on purpose with my friends, and once or twice, I simply had trouble sleeping.

i've always had a problem with sleep :/

^ Same. I will become fearful for no reason. I'll just get this feeling, like something (mostly of a supernatural nature) is going to hurt me. So I end up either distracting myself with a book or the net. Or I'll try to sleep with the lights on which doesn't work so I figure I may as well bet up and so something productive.

Only once, and it was at my friend's 18th birthday party. We were either swimming or sleeping in tents. I just sat pool side half the night then went n to a tent and talked to someone until like 5 am. After that I just went pool side again and watched the sun rise with people who pulled all nighters as well.

I work 2nd shift so my sleep schedule is already vastly different from most people, but I'm asleep by 3am every work day. Only on the days I don't work do I stay awake all night.