It might be a fad on the day of the IPO, but if you break Groupon's business model down to its essential elements, it requires a huge number of leaps of faith to rationalize its competitive advantage and revenue potential. Goldman Sachs says they predict 40% growth year over year for the next two years. That sounds extremely fishy to me, given the already-dubious value of the service, the low technical and financial barriers to entry, the lack of loyalty from merchants and consumers alike, the allegations of crooked books, the early cash out for founders and investors, etc., etc. Too rich for my blood, I guess.