On amazon at least, it's possible to counteract this effect using 3-star reviews. The kind of people who dislike a product but aren't vindictive about it and still see its strong points tend to be even-tempered folk.
I could care less about a bunch of unwanted emails in my inbox, but the pollution of the online community review and advice spheres is what really pisses me off about cnuts who try and game stuff.
They're polluting our collective consciousness quite literally.