Well, I can tell you from using their API's that Google doesn't necessarily use them.

I don't recall that specific scenarios, but over the past year I learned this with the maps API. As long as you're hitting a real endpoint, then it will return 200 - even when there are errors and it should clearly return a matching http status code.

I suppose it so the same API could be implemented in any given protocol, however, I don't think that is useful in many cases.