Depends on your jurisdiction, of course. (I am not a lawyer and this is not legal advice, merely my impressions). In the UK this would likely be worth it if the injury is a specified financial amount. So for people who have paid for something and simply not got it, a small claims court is a good bet for getting a refund. A lot of the time however, the injury is in the consequences of relying on one of these companies services, and having it withdrawn without notice, as in the OP. Usually, you want service restored, as that is in fact the least costly action for both sides. But small claims courts (in the UK) do not make that kind of order. In theory you could sue for the financial consequences of the abrupt withdrawal, but I'd guess that's too complicated for a small claim.

You'd have to go in the same jurisdiction as they're incorporated. I think (IANAL).