Unfortunately, whether Groupon is the "ultimate lesson in the dangers" of this type of growth-at-all-cost business or a validation that you can make a shit-ton of money being a founder or early investor of such a business (while leaving others to hold the bag) depends upon personal perspective, whether or not you've got a chair when the music stops and how willing you are to be ethically, morally and in some cases legally flexible in the pursuit of personal wealth.