A bit of a vicious cycle.
Why? It's not like you have to invest anything into the service (building a network, creating a profile etc.etc.) and it doesn't seem like a tool that is meant to become part of your workflow (e.g. reader). Also, if Helpouts goes away these 'experts' will still be available somewhere - you could schedule appointments directly.
I doubt it. That attitude is mostly a HN/geek thing. I like that they're willing to try things and test for viability in the real world. I'd rather have something and for it go away than to never have it at all. (And yes, I do understand the frustrations with Reader but I wouldn't go back in time and never use it from the start)
But that's true of any service from any company. If I'm a stay-at-home mom making some extra cash on Helpouts, I have a very different risk profile than a doctor who closes down his practice to see patients exclusively through Helpouts. The stay-at-home mom might not be happy about a shutdown but she still "[netted] a lot of money" whereas the doctor might have destroyed his/her career. Every individual/company needs to assess their own risk and take the appropriate risk-mitigating actions.
The point I'm making is that the damages from a Google service shutdown are typically very low or easily mitigated (Google Checkout being no exception) and every service should be evaluated on an individual basis with your risk profile. If the value you are getting from any service is lower than the damages that would result from a shutdown, don't put all of your eggs in that basket; if you do anyway, get some contractual guarantees and be confident that they will be fulfilled.
In that case, no services that Google offers should be used. They don’t give any guarantees, not even to their paying customers.