Most people seem to be missing the most important point:
Monetary gain is proportional to risk, not effort.
Unlike what the designers of World of Warcraft would have you believe, you cannot become a billionaire simply by doing mindless repetitive tasks. Even if you're one of the top experts in your field, getting paid a $500k salary, that's still not going to make you genuinely "rich."
To become extremely financially wealthy, people have to take extreme financial risks. They have to invest in something, whether that be stocks, real estate, or their own business.
There's one loophole in programming, and that's to create some piece of software that's so sought-after that a major company like Yahoo or Google buys it from you (think YouTube). That takes very little risk (unless you count your personal time as an investment), but it also imposes a hard limit on the potential reward. These monoliths don't pay you royalties, they either buy it outright for an amount that's riches to you but chump change to them, or they make their own and put you out of business.
Problem is, there are so many people trying to access that loophole today that you have to have a really brilliant idea, otherwise chances are it's already been done (better).
Lots of programmers seem to be investing in the stock market these days, and the ones who are good at it probably get rich. And of course, you have a dozen examples here of programmers who started their own businesses; they get rich too. I can also point to many programmers and engineers who do expensive consulting and make quite a pile doing that - but in order to get there, they also had to take significant risks, quitting their full-time jobs and working for peanuts to establish reputations.
The common thread is that programmers do get rich, but not just from programming and sweating for the Man. Like any other profession, in order to really hit it big, they have to put their money and their credibility on the line.