For all its success, Groupon has apparently left a trail of dissatisfied merchants.

Travis Kalanick, CEO of the online car service Uber, is among them, and he has thrust himself into the spotlight as the voice of these unhappy business owners.

During a South by Southwest panel, in which Groupon reps were scheduled to discuss the company’s annoyingly self-serving approach to copywriting, Kalanick spoke about his negative experience as a Groupon client.

From Fast Company:

He said that Groupon representatives had promised him primary placement and not delivered, didn't run the offer on the dates he wanted, handed him a data dump in a clunky Excel spreadsheet, and gave him an initial estimate of proceeds from the offer that was ten times higher than what the group deal actually delivered.

Darren Schwartz, Groupon’s VP of sales, had the unenviable task of doing damage control in the wake of Kalanick’s PR bomb.

The message was simple: They’re working on it.

And just when you might think that response would suffice, Schwartz went and screwed everything up, telling Fast Company, “We want to help them not only understand how to use Groupon but how to run their business better.”

So, let’s recap. Groupon, which admits it is having its own trouble running its business, wants to teach its clients how to run their businesses better.

Perhaps there’s a Groupon out there for half off any muzzle.