add to that, the primary cost of youtube is probably bandwidth; and I believe Google probably pays less for bandwidth than anyone else; Google is uniquely suited to make the YouTube model work. On the other hand, the big cost for groupon seems to be salespeople. Unless google can replace flesh and blood salespeople with something automated, that wouldn't be nearly as good of a fit. Google doesn't have cheaper fleshy sales people than anyone else.

edit: on the other hand, what if google was buying the fleshy sales people? what if that is what they wanted? I mean, groupon is doing okay at penetrating the small local business market in a way that google isn't.