This has become a serious problem on IMDB as well. It's common, almost the norm for small releases, to have a flurry of reviews right at release giving ratings

This has become a serious problem on IMDB as well. It's common, almost the norm for small releases, to have a flurry of reviews right at release giving ratings of 8 or 10 out of 10. They'll have glowing comments about how the director made such effective use of a shoestring budget, and so on. And then a little later this gets followed by a string of 1- or 2- out of 10 reviews, saying it's one of the worst movies ever and the high reviews are obviously shills. For larger movies, or over a large enough timespan, the noise eventually gets drowned. But it's made IMDB reviews useless for deciding whether to watch new movies.