I wonder how much due diligence Google puts into verifying DMCA notices beforehand. And if you wanted to do it "legit" you could create some works with search terms you wanna censor. So like, "Hotel Reservations in X", a photograph of a Ramada Inn. Then get these takedown firms to go spam notices like Wicked did here, and collateral damage ends up removing some of your competitors.
The DMCA is deliberately designed to discourage recipients of takedown notices for doing any verification beyond that the notices ate in the correct form before complying, since the safe harbor only applies when a proper (in form) notice is complied with and there is expressly no liability that can attach for complying with a formally correct notice that is substantively incorrect.
So I'd assume any due diligence is directed at formal correctness rather than substance as any other approach would have added cost to implement while increasing legal risk.
