I think of it this way: Suppose you don't have exceptional abilities. If you do what is prestigious, what "seems" like it will get you rich, what other people tell you to do -- then you have roughly a 0% chance of getting rich.
If you take a slightly unusual path, enjoy it, and get the flywheel/positive feedback loop going, you have maybe a 1-3% chance of getting rich.
So if you want to increase your chances of getting rich, I would do something that others aren't, and do it to the point past where others would give up, because it's not making them any money.
The thread is over if you want a repeatable way to get rich. There is something analogous to the "no arbitrage" principle for personal income. If there were an easy way to get rich, someone smarter/earlier/luckier than you has already taken it, and they didn't tell you about it until afterward. You have to find your own way.
Probably not repeatable ways to get extremely rich.
This post from Cal Newport elaborates further[1]. I highly recommend his book So Good They Can't Ignore You.
[1]http://calnewport.com/blog/2010/01/23/beyond-passion-the-sci...
That would have ruled out Google (AltaVista) and Facebook (MySpace).
Thiel's premise is to be the last search engine, the last social network, etc. It's not: don't enter competitive fields; it's: compete, best the competition, and become a monopoly. There's no such thing as avoiding competition, there is no scenario under which Google was going to not have to compete, and have the entire market handed to them. The question is: can you acquire market dominance or not?
If Google had wanted to compete, it would have gone for Yahoo, and become a portal, and tried to maximize user time on the site. The conventional wisdom was that Yahoo was far more worthy of competition than AltaVista. AltaVista wasn't even a company; it was almost shut down by its parent company IIRC. And it didn't make any money. Nobody wanted to compete with AltaVista. Search was viewed as a feature, not a company.
Facebook also avoided competition in its early years by being closed to the public and signing up one college at a time. They formed monopolies on social networks within specific colleges, and leveraged that position to expand to the rest of the world.
The idea is not to compete "head on". Don't just try to do same thing, but better. Do something different. It's hard to imagine what the world was like before Google or Facebook, but they were both doing something radically different early in their lives.
[1] http://www.wsj.com/articles/peter-thiel-competition-is-for-l...
Read Peter Thiel's Zero to One. He talks about competition vs. monopoly. You want to do things that other people aren't doing. He talks about the Harvard MBA grads who chase the last bubble, i.e. getting your timing exactly wrong.
People don't get rich by doing things other people told them to. And people don't get rich by doing "prestigious" things either. Read the parts here about prestige -- it's dead on:
http://www.paulgraham.com/love.html
(BTW this is also coming from someone who "got lucky" -- can retire in my 30's but never thought about money.)