It's just a particular way to analyze some data on oDesk, I wouldn't take it as a gospel of pure truth.
I want to find out about the tried and tested niches that HN readers might know about.
Background: my goal is to find some in-demand yet rare skill and hammer the crap out of that so I can get paid more per hour and cut down the percentage of my life that is spent generating income for food, shelter, clothes, etc. Working 40 hours per week doing boring C# code is very inefficient when I have so many other projects that need to be done. And for the time being (ie until I build the next Facebook :)) I think consulting will be the best way for me to reach my objective.