A useful post on www.marketresearchtech.com titled Fake Survey Software Reviews (How to Spot) provides some interesting suggestions on how to spot fake review sites.

Highlighted are a number of things to look out for but they main thing to be aware of is that fake review sites do exist and they are increasingly becoming pretty good at hiding their true motives i.e. to push a particular product. The best advice is to stick to mainstream review sites or active forums/blogs where it is clear that what you are reading is unbiased or at least the author has divulged any vested interest they may have.