This just stinks of another way to abuse the talent. If you want to pay someone below-market rates to fix your business's problems, there are already a multitude of race-to-the-bottom "contracting" sites to suit your needs.

Real consulting at market (or even above-market) prices exist for a reason. The kind of people who will spend hours setting up a consult, to only officially charge for 30 minutes, are exactly the kind of people you don't want working for you, for any period of time. You get what you pay for.

I can't for the life of me imagine what an apparently legitimate "micro-consulting" gig would look like, where the talent being hired isn't being asked to overperform for the amount of billing time being requested.