I have over 1,000 contributions on TripAdvisor and try to be fair, but will leave a negative review if we've received genuinely poor service.
A common theme for negative reviews that I've noticed is the people who show up hours before check-in time (as in, before check-out time for the previous night's guests) and are righteously indignant that they have to wait to get in their rooms. One woman complained in particular about being forced to hang around the lobby with nothing to do. This was a hotel in downtown Boston, next to a big . I'm quite certain that the hotel would have stored her luggage while she went to the Prudential Center mall, literally next door to the hotel, or walked around to see the sights. I'm quite certain that no one from the hotel tied her to a chair in the lobby and made her wait, but she was "forced" to do so.
The reviewers who really annoy me are the negatives ones who start their review by stating, in so many words, that all previous reviewers who enjoyed a restaurant or hotel and gave it favorable reviewers are ignorant morons who don't know what they're talking about.
DH and I decided to break up a long driving trip this spring by stopping at the halfway point, which was a motel next to a race track (harness racing). For dinner, we have made reservations at the track's nicest restaurant, which had tiered rows of seats with views of the horse races, TV monitors at every table so you could watch races from other tracks, and a three-course prix fixe menu for $39.99. We had a blast. The food was great, it was fun to watch the horse races, and we enjoyed chatting with people at nearby tables who were real fans of the sport. The track had recently renovated the grandstand, and the restaurant had just re-opened under a new name.
I gave it a great review on Trip Advisor -- as I said, we really had a great time. Because it had just re-opened under the new name, mine was the first review it got. Two weeks later, another reviewer left it a very poor review. He and his family had had a very poor time (in part, I think, because he brought children who were perhaps too young for this particular place). I can understand that. Every place has an off day.
But, what annoyed me, is that he started his review, "Where shall I begin? Obviously the previous reviewers never ate out before this". Well, there was exactly one review before his, and my posting history clearly shows that I eat out a lot. (Our neighbor once told us that she thought it was so sweet that DH have date night every Saturday night and go out to dinner. We didn't have the heart to tell her that we're just too lazy to cook.) But, yeah, he had a bad experience, so everyone else who had a good experience must be wrong.