I wonder what that really means? Google probably isn't going to go combing through all their accounts to remove channels they think are so full of crap that there won't be ad revenue for them. It seems like it might another way of saying that if your account is doing something unsavory/bad/whatever, they might decide to remove it in that case, if it happens not to be commercially viable for that reason. Though there are other aspects of the terms, I'm sure, that prevent you from doing stuff that's illegal/etc., so I'm not sure why they need this....