There are many, many stories of bad (and incriminating) behavior on behalf of Yelp salespeople over the phone, but I have never heard a recording. Even though most claims indicate that the harassing calls are repeated many times. Somebody record one of these calls and become Internet famous!
There are also many stories like this one that should come with before/after screenshots or links to an archived page. They need to actually link to the page in question so we can see if they are accurately depicting the situation. Shill reviews are easily spotted by people who have the necessary experience.
Like I said, I am ready to turn around on Yelp, these stories sound very plausible to me. I haven't yet seen sufficient evidence. The fact is that I do use that service and the subset of restaurants that I know very well have reviews that match my experience with the place. Therefore I can't help but think that perhaps the person who write the linked article is perhaps deserving of bad reviews and doesn't want to admit it.