I get what you're saying Rob, and you're right, but I think that when an affiliate uses the term "scam", whether in the "this is a scam...NOT" sense or the "product xyz scam? read my review" sense, they're just using a tactic which falls into a grey area to get attention to their ad or website.
If a non-affiliate asks if something's a scam, then it could generate a good discussion, yeah. But if an affiliate does it, then I personally don't think it's fair to the product owner. Even if the review is glowing, which they usually are, seeing the word "scam" associated to a product will lead some people to get funky ideas.
Maybe it's just me, but I'd rather not see people using that modifier in their affiliate campaigns.