For a more credible source Kaushik Basu wrote in a 2014 World Bank working paper on Ponzi schemes:
One of the most recent cases of bubbles occurred in the new ‘Bitcoin’
experiment. Bitcoin is a crypto currency, the main and original attraction of which is the low transactions cost associated with its use. One can buy Bitcoin the way one can buy euros and trade freely with others having euros. Trouble started when people began speculating that the value of Bitcoin would rise, thereby raising the demand for Bitcoin and making the value-rise a self-fulfilling prophesy. In other words, what we witnessed recently in the Bitcoin phenomenon fits the standard definition of a speculative bubble.
Contrary to a widely-held opinion, Bitcoin is not a deliberate Ponzi. And
there is little to learn by treating it as such. The main value of Bitcoin may, in
retrospect, turn out to be the lessons it offers to central banks on the prospects of
electronic currency, and on how to enhance efficiency and cut transactions cost.
Which is not to say there aren't other crypto-currency-shrouded Ponzi schemes, there are, e.g.:
OneCoin’s “blockchain” consisted of little more than a glorified Excel spreadsheet and a fugazi portal that displayed demonstrably fake transactions
Nor is is safe to say that anything related to Bitcoin itself is not a Ponzi scheme, in particular, the SEC found Ponzi fraudsters operating bitcoin-related schemes:
In a recent case, SEC v.
Shavers, the organizer of an alleged Ponzi scheme
advertised a Bitcoin “investment opportunity” in
an online Bitcoin forum. Investors were allegedly
promised up to 7% interest per week and that the
invested funds would be used for Bitcoin arbitrage
activities in order to generate the returns. Instead,
invested Bitcoins were allegedly used to pay existing
investors and exchanged into U.s. dollars to pay
the organizer’s personal expenses.
That kind of fraud can be done with pork-belly futures, by the way, there's nothing crypto-currency specific to it. There is one kind of more technological fraud related to bitcoin:
The complaint, filed 1 December 2015, alleged that the companies offered high-spec mining operations with the power necessary in return for investor funds. However, SEC said that GAW Miners and ZenMiner did not own enough computing power for the mining they promised, and as a result, "most investors paid for a share of computing power that never existed."
That's selling the Brooklyn Bridge in digital form, basically. It turns out there's even an academic survey of Bitcoin-related frauds, quoting from the abstract:
We present the first empirical analysis of Bitcoin-based scams: operations
established with fraudulent intent. By amalgamating reports gathered by
voluntary vigilantes and tracked in online forums, we identify 192 scams and categorize
them into four groups: Ponzi schemes, mining scams, scam wallets and
fraudulent exchanges. In 21% of the cases, we also found the associated Bitcoin
addresses, which enables us to track payments into and out of the scams. We find
that at least $11 million has been contributed to the scams from 13 000 distinct
victims. Furthermore, we present evidence that the most successful scams depend
on large contributions from a very small number of victims. Finally, we discuss
ways in which the scams could be countered.