I have a piece of paper that tells me I'm an expert in some domains, and there are more than enough straightforward questions in my field I can't answer in 42 minutes, and certainly not for $4.20, even if I was just paid minimum wage.
Re your question about domains: sure we cannot cover everything at the moment. Other domains would work into our business model which will unfold over time. For the moment we'll stick to where we can bring most value :)
And my field of expertise is a tiny subset of "IT". The other two fields you take questions on are "Legal" and "Finance".
Do you really think you can any non-trivial answer in those extremely broad fields?