That's the mantra of conspiracy theorists, UFO forums, and Bigfoot communities. Let's give Yelp the benefit of the doubt before we assume that they are illegally extorting small businesses based on no public evidence.
BUT tort-law firms do NOT lightly make decisions about where to allocate resources when being the FIRST to move in a class-related suit.
Neither of the firms is huge or that well established, but I imagine that they have sufficiently compelling evidence in hand to proceed, and the point of doing a PR blitz like they’ve done is to find other pissed-off, potential clients which will only grow the pool of riches should they win.