Aussie - Thanks for reference. (Sorry to say, the particular link you posted is likely to be deleted because of WebmasterWorld TOS.)
Here are the original sources. I'm sure there were many tweets along the way as well, but here are main references to the story, and I'll included time stamps....
Sauce restaurant's email exchange with Groupon rep, who has since been fired, on Sauce's Facebook page... Sauce
August 16 at 5:21pm near San Francisco
WebmasterWorld doesn't quote emails. In this case, though the email has been published, I'll let readers view the exchange on their own. Here's how the Sauce owner prefaced the exchange...
UNBELIEVABLE CUSTOMER SERVICE EMAIL FROM GROUPON - Threatening me with Bad yelps for not letting him bully me into a sales pitch!
AllThingsD then picked up the story, and most references I've seen about the story quote AllThingsD. The titles are largely self-explanatory... Groupon Suspends Sales Rep While It Investigates Thinly Veiled Yelp Review Threat (Update) AUGUST 18, 2013 AT 9:45 AM PT
That was followed by a more extended story in the restaurant news blog of sfgate.com, the site of the major SF local daily newspaper.... Groupon manager allegedly threatens bad Yelp reviews after San Francisco restaurateur declines offer [Updates!]
Posted on 08/19/2013 at 11:41 am
And, along the way, another story in AllThingsD, with comments from a Groupon spokesperson.... Groupon Fires Sales Rep Who Threatened Negative Yelp Reviews for Restaurant Owner AUGUST 19, 2013 AT 12:20 PM PT
Aussie's comment up above gets to the heart of the matter....
great show of how social media can effectively push back
It's quite striking, and, you are right, companies ignore that at their peril.