Hmm. I think my counter-point would be that in this particular case the interviewee has a direct incentive not to tell the truth and a plausible alternative story provided for them by GroupOn's PR machine. Plus they know that whatever they tell the journalist can't easily be checked: it's not as if the journalist is going to get access to the books, at least not until after any bankruptcy at which point the whole thing will be moot.

I would surmise that these properties don't usually apply to most journalistic interviews. In this particular case it becomes difficult to know whether you're getting a true picture from interviewing GroupOn client businesses because the alternative explanation put forward by the author of the original piece gives the SBO a strong incentive to lie about their motivations. (Whether to an interviewer or to themselves is an open question!)

Another thought occurs to me: As you say, a good journalist can often find a way round these problems but in this particular case, where we're talking about a whole business model, it seems to me that a few counter-anecdotes will not have much impact: Believers in the GroupOn story will (rightly) be able to say, "well of course there are a few people mis-using GroupOn in this way, but they're a tiny minority & the vast majority of GroupOn customers are very happy with their experience dot dot dot" (I'm sure you can fill in the rest of the PR guff yourself).