I think you can check it out with bounty youtube campaign, well I haven't know very well about it but it seriously some of them does it, I've seen a lot of youtubers doing review of an ICO, markets etc.
Don't just invest based on these reviews because many of them may be posted just to earn some extra money either from youtube or from the campaign they participated. But that doesn't mean that you can't find any good reviews but you need to spend some time to find those real reviewers. Youtube is flooded with a lot of information but it is our responsibility to find the correct one.