Well, for CPA the only thing that matters you already know, then it's up to you to decide who you want to run those ads and if they agree with you and find you trustworthy. That's a 'solved problem' in the sense that for a long time such situations were dealt with using outside auditors. It costs a bit but not so much that it would make CPA impossible, merely less convenient.

Interesting part I got from this discourse: there is no 'one size fits all' when it comes to what is acceptable and what is not. That's yet another problem to be solved.