From CBC TV in Canada…
http://www.cbc.ca/news/business/yelp-google-and-urbanspoon-targets-for-fake-reviews-1.2826154
Not that I advocate it but since yelp extorts business one way, why wouldn’t business try this. You can not even ask for reviews, I asked our customers to comment in yelp and they hid all of them, no i do not advertise with them