Actually there are some pretty mature kids of that age. My nephew for one. He just turned 15 and got his ipod touch for Christmas. He is more mature than some adults I know. He is a little spoiled, but for the most part a great kid.
I'm 19, but I remember when I was on the internet at the tender age of 11. Used to have to fake the age just to get onto sites... Those were the days. I'm actually surprised how many people over 30 are on the site... Very interesting.