Reviews are only removed by the poster. We do not remove bad reviews at the vendor's request. When we are asked by a vendor to remove a review, we tell them that they need to work it out with their client.
Regarding posting great or bad reviews, I think that with things like wedding photography, most people that post reviews either really LOVE their photographer or really HATE their photographer.
If you feel that some reviews may be suspicious, flag them. We do have some filters in place but of course cannot verify every review.