You have no contract with Google though. You're literally siphoning on what is a really low-barrier, dare I say free service.

They didn't screw you over. You chose to use them. You didn't pay them, they're paying you.

If you don't like that arrangement, feel free to join a partner agency that can buy and sell ads for you on the ad exchange or go to a different ad network.

Then, if they do something you don't like, you actually have very real power to compel them to do something.

Remember, you get what you pay for.

Your contention is that someone can't screw you over unless you're paying them?