Jamie also worked under Peter Norvig, and this is what Peter said about Jamie:
". One of the best programmers I ever hired had only a High School degree; he's produced a lot of great software, has his own news group, and made enough in stock options to buy his own nightclub. "
-- from http://norvig.com/21-days.html
Once you build something as important as Netscape Navigator and cash out for a good chunk of money, I think it's ok to do whatever you want. Building something for the future doesn't have to be a lifelong thing.
Selling beer => flirtation => sex => sperm + egg = Building a future human being!
But seriously, Joel is on crack.