No, in most places it isn't. If a consumer was misled by a planted, phony review and bought an inferior product, he could go to civil court and demand monetary compensation, but civil courts largely deal with the kinds of damage claims that don't involve the legality of an action, only its harm.

Just remember that an illegal action would be prosecuted in a criminal court. A claim of harm would be prosecuted in a civil court.

Most of the activity surrounding phony reviews is not about the legality of the activity, but how much harm the public exposure might do to a company's reputation.

> I'm pretty sure paying for fake negative reviews of competition is illegal, because there is a clear victim.

Even in that case, it's not a question of "illegal" as much as misleading, and the remedies are usually civil, not criminal.