How would you be tearing someone down by saying YOU had a bad experience with X? The experiences are independent of each other, and what you would be doing is providing others with another data point that could help in their decision making process.
Telling people to ignore all emails is not the answer, because we often do get legit solicitations. What everyone really needs to do is some due diligence. You adding your experience aids them in doing that.
*Sigh* Fine. If only because somebody else will wind up doing it eventually. The culprit is "Red Headed Book Lover Blog". On the surface it really did look legitimate, so when she offered to review my book for a fee, and I couldn't find any negative comments anywhere online, I decided to chance it.
To be clear, the expectation was not "pay a fee, get a positive review". She claimed to have already read the Amazon preview and liked what she saw, and I have confidence in the quality of my work, so I anticipated that whatever she came up with would be reasonably positive.
The person was highly communicative and enthusiastic, so I didn't have much cause for suspicion. Unfortunately, when she finally posted the review, it was painfully obvious that she never read the damned book

It was a few paragraphs of gushing compliments and shallow tidbits of information easily obtained from the Amazon page. Also, my dashboard didn't register any sales during the period when she would have downloaded it.
In all honesty, somebody who didn't know my book might be fooled. I could probably dangle that review in front of some people and get a few sales out of it. But it would be a scam, and I'd know it. So I consider the whole thing unusable.
Anyway, the Kboard member who pm'd me thought to Google search the whole blog, and found that the blogger re-uses the same lines over and over in different reviews. So basically anybody who paid for one probably got taken, and hence the reason I wasn't eager to be the bearer of bad news. Sorry for any hurt feelings this may cause.