Anyone else dealing with these ads that yell scam at everything and then promote some really shady things on the landing page? I've got several of these scam ads on one of my keywords. They aren't customers, they claim scam and tell you to visit for the "truth". They make a page trashing the product and then offer a link to their "legitimate" product.
Most of them turn out to be e-gold/ecurrency, the latest $1000 pyramid scheme or data processing. In my case it seems to be coming from scam-alert and gurubusters justicereviews and a few others. So far google hasn't banned them even though data processing and e-gold offers are in violation of their own policies. Maybe google hasn't seen the child porn charge against e-gold? Seems really odd that they would allow this at all.
"Don't Get Scammed" is just as legitimate of a call to action as "Buy Now", regardless of the content of the page or underlying intentions. Banning such copy from ads would be a slippery slope (yes, the old slippery slope argument). I may get flamed for this, but crying "scam" is just a more aggressive version of a product comparison... they're creating the perception of flaws or shortcomings in the competitors' product in order to cast their own in a more favorable light.
That being said, I've seen plenty of these ads too. None in any of my clients' industries, but I know the ones you speak of. I don't like them any more than you do in most cases, but I don't think the problem is widespread or sinister enough to generate the volume of complaints from advertisers that would warrant a policy amendment.
If my keyword had anything to do with a biz opportunity then maybe I'd agree that they belong there. But these ads are totally irrelevent to the keywords I have.
The only relevancy is that they scream scam and place a some type of opinion on their site, beyond that there is nothing except "buy my scam that has nothing to do with what you were searching for". Notwithstanding the fact that these "opportunities" are prohibited in Google's guidelines...