A WebmasterWorld thread shows how a webmaster is sad that his competitor out ranks him. This webmaster is upset because he feels his competitor is outranking him due to the number of complaints his competitor has. Since he has so many complaints, he is getting many links from people pointing to his site, complaining about him. The links are helping the site rank higher and thus get more complaints, which leads to more links.
Here is the webmaster's complaint:
One of my competitors has apparently scammed lots of people. So webmasters and forum participants post things like "Beware of
X Y Z. They took my money and I never heard from them again!" Where X Y Z is a very lucrative keyword. X Y Z's site sucks really bad, and it has practically no value for that keyword, but they are still ranked #2.
In fact, by having those anchors and being ranked so high, they get to scam more people!
Clearly, there can be other factors this webmaster is missing. But there is no doubt, that honest reviews, good or bad, can lead to good quality links. Even if the review is bad, it would be hard for Google to say - hmmm, this is a bad review, I'll rank the site lower. In fact, Google tends to like negative reviews high - or at least, those are the type of sites that get a lot of attention from me.
I wish I had more time to delve into this thread but it does make for a good discussion.
Forum discussion at WebmasterWorld.