I would reach out to them, though only to get their contact info. Anything that may be personally identifiable would be great. I'd also record the conversation.

I would reach out to them, though only to get their contact info. Anything that may be personally identifiable would be great. I'd also record the conversation. Then I'd take it all to the FBI. I'd also send it into Yelp, they'll probably remove the offending posts if you've gotten all that. Extortion is just as illegal on Yelp as anywhere else. Of course as many mentioned here, don't pay. They'll just do it to you again if you do.