I am not at all a Groupon apologist (I think their base business is declining and doesn't make sense for most local businesses in the long-term), but you have gone way overboard by comparing Groupon to boo, webvan, and kozmo.

For all its faults, Groupon is on track for $1.5Bn in NET revenues (this doesn't include pass-through that they initially included in revenues) this year, and will probably still IPO somewhere around 10 billion dollars. All of the companies you mentioned only existed for 2 years before being liquidated.

As for everyone in the valley knowing Groupon was a ponzi scheme for the past year and a half - then the folks from Battery, Accel, Kleiner Perkins, Greylock, NEA, TCV, Silver Lake, etc (all of whom made investments in Groupon this year) would have to be complete idiots to invest in Groupon, and that is certainly not true.

Sidenote- a quick reminder on what it was like in the 00 bubble that you reference: http://feefighters.com/blog/ff_infographic/tech-boom-or-bubb...