I'm 100% self-employed and build websites where I earn money from advertising/affiliate/sales-revenue. Been doing it fulltime for 7 years now, before that I was a student for a couple of years (where I learned that me and academics wasnt a match made in heaven..).

I used to have a site that carried 5m uniques/month, but I've also run sites that had has worse performance problems with much less users. I know of several instances where I got stuck and had help from academic books (to refresh my memory) or friends that paid more attention in class than I did :-)

My point, and as others point out, you just dont learn these things yourself unless you are forced todo it. Learning to solve a problem and learning to learn are two very different things and the later makes your view of a issue much more complete. Many subjects is completely useless stuff that is only in the courses to make them hard, but when I look back I tend to see that many courses were very valuable.