I think this is a vocal minority. Sure, you hear all the time about this random biz owner who thinks Yelp is out to get him, but that doesn't account for the hundreds of thousands of biz owners who have claimed a free account and not cried afoul.
A more likely explanation of "extortion" is that the sales org hires 21 year olds fresh out of school who routinely don't make it past 90 days. I'd imagine some of these reps might resort to shady practices to fill a quota, but that's also why they don't last past 90 days. I think this is just a problem of needing a sales organization to make money.
Disclaimer: I used to work on the engineering team at Yelp, and I have the utmost respect for the intelligence and morality of the engineers on the review filtering team.
I'm willing to postulate that the shady tactics are originated by the sales reps, but not that Yelp isn't responsible in that case. Tolerance of a culture of unethical sales, creating an incentive & hiring structure that encourages it, and being obstructionist when someone who encounters it tries to get their issue dealt with speaks rather more to complicity than innocence. As further anecdotal indication (since you appear to believe that all complaints are isolated and don't appear to have any threshold at which you'll accept otherwise), my girlfriend's cell phone was listed as her restaurant's phone number and she was told repeatedly by support staff, sales, and supervisors that Yelp would not under any circumstance correct this unless she paid for an account. Since her place was open from 6pm to 9am and she had to have to phone on in case of emergencies there, she got calls all night long seven days a week. The only thing that fixed this when she was at the point of involving her lawyer was a random Yelp employee who frequented the restaurant hearing about it. If a single internal comment is enough to fix it, but a legally actionable case (non-public number acquired from a review, refusal to address, telemarketing calls to it) gets "sue and be damned" I'm inclined to think that the company has a major issue at the interface with businesses. She literally did not care what the reviews were because word of mouth in a couple of communities was far more important, but they kept trying to sweeten the deal by offering to "fix" the negative ones.
A more likely explanation of "extortion" is that the sales org hires 21 year olds fresh out of school who routinely don't make it past 90 days. I'd imagine some of these reps might resort to shady practices to fill a quota, but that's also why they don't last past 90 days. I think this is just a problem of needing a sales organization to make money.
Disclaimer: I used to work on the engineering team at Yelp, and I have the utmost respect for the intelligence and morality of the engineers on the review filtering team.