High growth is not a ponzi scheme. High growth with no value is. Going flat is fine, Google did that.
Losing a lot of traffic because people stop using your worthless site entirely is bad. Groupon will do that.
No its not a Ponzi Scheme is a type of fraud where the con man pays out early investors from proceeds from later investors.
I've derived quite a bit of value from Groupon myself, as have several people I know. They failed in execution because it appears they don't value their relationship with vendors as evidenced by not letting them impose limits in the number of coupons sold. Mom and Pop restaurants don't scale like startups and many were left with really bad experiences from being ill equipped to deal with a massive influx of customers in a short time frame, and consequently the customers ended up having a bad experience as well. This wasn't universal but it seems to have been frequent enough to have severely tarnished the brand. If Groupon had been better stewards of their relationships with their merchants instead of sacrificing them in the name of growth I don't think anybody would lump them into the "ponzi scheme" camp. Groupon could have gone about it differently, Bernie Madoff probably could not have.
That sounds an awful lot like zero-sum thinking.
Should we make one up right now?
Cells in a petri dish can exhibit a behavior where they grow quickly, consuming the sustenance where they are, and expanding outward in a rapidly growing ring, as the middle starves, until the landscape is consumed and everything starves. The XScreenSaver "GLCells" [1] is a simulation of this effect. By all the simple metrics like cell count or cell mass, everything looks great... until it's not.
A biology expert may be able to tweak this. If this phenomenon has a specific name, that would be even better, but I doubt I can google it up.
(Incidentally, I'm just offering this up as a term. I think the title is premature; it has not been proved that this is the case for Facebook. If we are going to speculate that they may in the future not be able to continue making money as they are today, they still have a lot of runway. I'm not itching to buy shares, but I wouldn't personally guarantee they won't be able to make money.)