I dropped out at 20 as a Junior in college. I had scholarships to school and every reason to stay but I was already working long hours on a business I had started as a Freshman and had no intention of slowing down.
We were growing, by my nineteenth birthday we had 13 employees and by my 20th I got my first acquistion offer.
I decided to take one of those offers and as a condition of it had to consult for the company I had just sold to for a while(turned out to only be 8 months).
So I made the decision to drop out and pursue this opportunity.
There are days when I regret leaving school for a number of reasons, not the least of which is that I never really got to be a kid or act like my fellow classmates, however NONE of the reasons I regretted it has to do with not being about to find work I like or chase my dreams.
I recently went through the Winter 2012 YCombinator class(and subsequently left the company as well) Then was picked up by a well known company in the ruby community almost instantly and have continued to be able to find work at levels which I cannot handle.
I run a boutique consulting firm and have for quite a while. I usually do one or two projects a year that amount to anywhere from &125k-$300k. I almost always turn a few projects a year down and rarely do I ever get bored or have nothing to work on.
I think the major difference between the people disappointed they dropped out and the ones that aren't is motivation.
It does not matter how bad you want something you still have to work for it.
The people who sit with their hands on their asses and complain they did not get things handed to them get no sympathy from me.
I grew up the absolute epitome of middle class and have fought my way out of there. I make no apologies for my mistakes and I rarely give up on anything. I think its fair to say most peoples successes or failures lie solely on themselves.
EDIT: I noticed I never said my age(I'm 25)
and also when friends of mine or people who know my story ask me about dropping out or say they are considering it, I almost always tell them DON'T DO IT!
I think there is a place and a special set of circumstances for dropping out, but its not for everyone and certainly not everyone who goes that path is as fortunate as I am, much less as fortunate as Mark Zuckerberg or Steve Jobs.