Here is an example: One Yelp employee had his friend write a negative review for the business that said 'no' to Yelp extortion/tax.
https://www.youtube.com/watch?v=gQAAauJlPq0
Yeah, this is a perfect example of why Yelp is not instigating this.
Do you really think Yelp is asking their employees leverage their friend's network to leave negative reviews or do you think this sales guy is at risk of losing his job for not converting enough and so he on his own asks a friend to help him keep his job?
If Yelp wanted to extort businesses, they wouldn't need employees to ask their friends. They could just adjust the search ranking to down rank businesses that don't want to pay.