Apologies if I'm missing this in the article, but it doesn't seem to take into account the level of demand for those skills. It's all very well having a skill that demands $50/hr, if openings for that skill only come up once in a blue moon.
You're right---there's nothing about the demand side yet. That's my next blog post. I'll show the earned wages by skill and some measures of demand & trade volume in different skills.
John - Can I get a link to the "controlled, centralized vocabulary of about 1,400 skills"? Not finding it anywhere I've looked.