Watching this makes you wonder what stops all companies from responding this way when they screw up. Is it really something as cynical as the lawyers running the show? I don't get it. A heartfelt apology goes such a long way towards rebuilding customer trust, it's a shame that more people aren't willing to lay it on the line like this. Compare this response to Kevin Rose's handling of the Digg v4 disaster. We all know what happened in the latter case, but I wouldn't be surprised if this helps, rather than hurts Groupon.
A lot of people cannot accept the fact that they or those under their command commit mistakes. Even if they didn't do it personally, they have to take personal responsibility for those under them, for the good and for the bad.