Apparently, suing them for libel laws is impossible because of CDA, but suing them under RICO might work. CDA says that you can't sue someone for content posted by their users. RICO is an anti-mafia law that says if you are part of an organization that causes illegal things to happen, you could also be liable.
I think if one were to try to sue them, one would have to mount an attack along this vector. The editorial nature of their review system could be seen as a generator of new content (even if it is based on used-submitted content); the end result (in terms of message and tone) is considerably different to the initial material.
I wonder though if such an approach has any legal merits. I've heard of something similar with copyright, where aggregating data for example and presenting it in new ways is copyrightable. I think one could expand upon that approach and use it as a basis for the complaint.
http://www.seomoz.org/blog/the-anatomy-of-a-ripoff-report-la...
Apparently, suing them for libel laws is impossible because of CDA, but suing them under RICO might work. CDA says that you can't sue someone for content posted by their users. RICO is an anti-mafia law that says if you are part of an organization that causes illegal things to happen, you could also be liable.
(IANAL)