When I see all the posts telling you "what would you tell your younger self", that's what I think (at the age of 25, working full-time while attending graduate school part-time and dating somebody an hour's drive away).
When you're a full time student... you don't know how great being a full time student is in many ways: not a worry in the world, you just manage your course load; you select the time of your courses, deadlines are reasonable and set ahead of time. On top of that if that there are smart and inspiring people for you and plenty of courses that you can take just for the hell of it (I really miss taking history and philosophy courses).
Of course it's easy for me to wax nostalgic about the great college days when I just drove home (to an 830 sq ft apt all to myself!) in a sports car I purchased new, after dinner at an upscale Indian place -- I am tempted at times to just take a leave of absence from work and do graduate school full time -- but once you're used to a certain lifestyle it's not easy to go back and cut your spending drastically.
Right now, I'm learning Processing in one class. I'm not learning anything new about language: I already know Java. Processing isn't used as much, and from what I've seen it's not doing anything that I want to do. We learned Scratch, which is a childish language, and ActionScript, which I've already worked with. I love learning new things; what I don't love is being in a place where I'm not learning and have to do busywork, while I have an idea and think I can mess with it. If that goes wrong, I'll know enough to find a program that teaches me exactly the thing that I go wrong with, and next time I'll be more prepared.
That's not to say everything that you study will be meaningful and exciting. There's tons of busywork in college (especially in the first few quarters, when they're bringing the slow kids up to speed), but that's life! If you think you're going to escape busywork by starting a company, you're being naive.
More to the point, if the stuff you're studying is so boring and unrewarding that it makes you want to quit, then you've got plenty of time to work on side projects while things get more interesting. That's where the free time comes from!
Looking back on it now (and having had to implement many of the algorithms we learned about in that class in C, Java and other languages that are less suited for it), I wouldn't have been able to grasp many of the sorting, binary tree or hashing algorithms nearly as easily in another language.
To my own surprise, one of the things that I now consider most valuable about my undergrad degree was that it forced me to at least grasp Scheme and Smalltalk.
* Bill Gates had the resources of an extremely well-connected and wealthy family to hedge his risk. He has also repeatedly and publically advised young people to stay in college, and not follow his path.
* Mark Zuckerburg didn't leave college until Facebook was growing so quickly that he had to make the choice.
* Larry and Sergey were grad students; they were trying to get their doctorates, not their BS degrees.
Ignoring all of that, there's some serious selection bias going on: for every Bill Gates, there are ten thousand droupouts who are flipping burgers.