IMO, even if it isn't true that Google has banned people for illegitimate reasons, it's entirely possible that when they do find a reason to ban you they sit on

IMO, even if it isn't true that Google has banned people for illegitimate reasons, it's entirely possible that when they do find a reason to ban you they sit on your account so they can take what you would have made and keep it along with their normal cut. It seems pretty iffy overall, but in their TOS for Adsense there is the line "If we terminate the Agreement due to your breach or due to invalid activity, we may withhold unpaid amounts or charge back your account." I think it's also worth noting that it can be trivial to get an account banned if you just get a few people to keep clicking the same ads all day. So 'legitimate' bans could happen even when there was no foul play from the person showing the ads.