If nothing else the timing of this seems suspect to me. The Linked In IPO has investors who missed out champing at the bit for something else. I think Groupon knows their current business model is unsustainable and have picked this moment precisely because the market is particularly irrational right now. (Note: I'm not saying there is a bubble in general, just that the Linked In IPO has created a unique opportunity for them to go public with less scrutiny than would otherwise be the case.)
I think Groupon is a suspect company to begin with. It's a great idea, but most of the last few rounds of funding have gone to pay off the early investors.
