Same goes for Facebook or any other big company. If your application depends on them heavily, then they can shut you down with the flip of a switch. If you're not making them money directly, they won't care either. I make the distinction between big and small companies here because if you depend on a small company, there's a lot more chance of opening a dialog and working out some kind of arrangement.
That said, to not hinge the entire outcome of your company on another company is, I feel, business 101. Doing so is a very high risk.
My feelings go out to the guys who started the company though...mistakes or not, it would truly suck to see all your hard work flushed down the toilet.