This is not a Ponzi Scheme.
Get your definition of Ponzi Schemes right, please. Ponzi Schemes are a specific type of fraud, not to be generalised to everything that relies on superficially similar principles.
Early investors in startups cash out during later funding rounds or acquisitions.
QED.
In a Ponzi scheme, there is a central party that refunds investors on demand, and does so with money from new investors.
A Ponzi scheme is always a fraud, frothy valuations in a bubble might indicate market manipulation, but not _necessarily_ fraud.
Right from the wikipedia:
"A Ponzi scheme is a fraudulent investment operation that pays returns to its investors from their own money or the money paid by subsequent investors, rather than from profit earned by the individual or organization running the operation"
Note that Wikipedia later in the article does clarify some of these points. To quote:
- In a Ponzi scheme, the schemer acts as a "hub" for the victims, interacting with all of them directly. In a pyramid scheme, those who recruit additional participants benefit directly. (In fact, failure to recruit typically means no investment return.)
- A Ponzi scheme claims to rely on some esoteric investment approach and often attracts well-to-do investors; whereas pyramid schemes explicitly claim that new money will be the source of payout for the initial investments.
In the case of Groupon founders cashing out, that was even publicly announced, and quite certainly not fraudulent in itself.
So startup bubble is a gambling scheme, not a Ponzi scheme.