Crime? No. But the whole point of a review site is the implicit promise to readers: "We will tell you whether this is any good or not". If what they actually do is to publish only positive reviews, for a fee, then they are deceiving their readers into thinking that advertisements are reviews.

Sure it's legal. All kinds of things are legal. Some legal things are harmful and dishonest, and should be exposed.

You're completely missing the point. There is a huge difference between illegal and dishonest. As far as I know, yes, it isn't illegal to pay for a published review but it surely is a dishonest business practice.

At the very minimum, this website is probably deceiving their readers by publishing these so-called "positive" reviews.

I never said anything about a crime. Reviews are only worthwhile if they are honest. I believe that any site caught soliciting pay to play for positive reviews should be called out. Not sued, just publicly shamed.

It goes both ways, Belkin caught tons of flack for soliciting positive reviews on Amazon Mechanical Turk.