At my usual $150 hour rate, it would take 17 hours on WageMachine to match one hour of work. I could just as easily spend those 17 hours finding that one hour of work (and it wouldn't be just one hour).
[Edit] Thinking about it more, I think your idea is very good, but lacks any real traction without being able to genuinely pay real experts -- I don't mean "highly talented, industrious, college educated, English speaking, and lives in the United States", but rather, someone who has at least a decade of work experience, is near the forefront of their field, and would like to invest some time in assisting, teaching, solving other people's once-off issues.
One of the primary reasons I don't participate in StackOverflow is that the vast majority of questions are simply boring. For $150, nobody is going to ask a boring question (and if they do, at least they're paying market rate for the answer).