Another thing they apparently do is let business owners (e.g. hotels) remove negative reviews because they're "defamatory".

I had a very factual 3-star review on a hotel that was supposedly very quiet, but was super noisy and the AC was not working. And there was literally nobody at the reception at the time of check-out and nobody picked up the phone either. All in all, nothing serious, but worth a review. Purely factual stuff, nothing bad-mouthed, just my experience and three stars.

A few months later the review was removed because it was "defamatory". I was able to get it reinstated by sending them proof of payment to the hotel and proof that I was there. A few months later, it was removed again! That same dance was repeated six times..... What a weird system.