Social Proof [1] in action. I'm always shocked at how much faith people put into anonymous review sites. Really? You're going to believe a bunch of strangers on how good something is, and actually spend money based on this belief? It's a marketer's wet dream. You don't need to actually prove a claim anymore: You only need to spin up enough sock puppets shouting about it, and people will substitute that for proof.

1: https://en.wikipedia.org/wiki/Social_proof