No, Yelp was extorting a friend's small food business. He had lots of 5 star reviews, but only a handful of bad reviews (supposedly made up) were showing up on the main page. Yelp contacted him at some point and offered to fix the reviews if he signed some kind of contract with them that amounted to around $2000 of monthly advertising on their site. He told them on the phone he couldn't afford that, he was a small business guy. Couple of days later 2 corporate guys in suits came down to his business, uninvited, to talk business which of course still didn't make sense, nothing had changed and he could not afford that type of money. He ran some numbers in his head and asked if they could send him business instead and make a cut, but their offer wasn't guaranteeing any new business, just crappy advertising on yelp. The bad reviews not only stayed on but started to multiply he turned yelp's offer down. Yelp is not anybody's friend and their business model is very unhealthy. I'm not surprised others review companies such as glassdoor resort to similar tactics. These are proconsumer in the beginning stages then they get corrupted.
Yelp is adamant that they don't affect reviews based on payment. That said the order and selection of reviews on preview pages in terms of positive vs. negative are based on how much a business pays.
Honestly, I'm sympathetic to Yelp. The money has to come from somewhere. And there's at least superficial evidence that you cannot operate a honest review platform at a reasonable profit rate (e.g., glassdoor, consumer reports).
It can come from advertising in-app/sponsored results appearing at the top of search. That's not extortionate, and doesn't compromise the whole purpose of using the app.
Either the ROI on those ads is terrible (Thus leading to low-margin businesses not advertising on Yelp), or they want more money, at the expense of long-term confidence in their website.
It's possible that the current, bloated version of Yelp, with a headcount of 6,000 cannot survive on search ads revenue. [1] It's also possible that a smaller, leaner version of it could.
[1] Facebook, by the way, employs ~40,000 FTEs. Facebook's revenues are 70 times that of Yelp's.
They moderate reviews that are inconvenient to the business that accept their extortion. Their business model is to sell protection to businesses, like an extortion racket.