The Monero devs are quite proud of the fact that it's the best cryptocurrency for scamming. It doesn't surprise me it's propped up by even more illicit work.

There are plenty of other shitcoins, like Ethereum, which started out with the creators giving themselves free coins during the early mining stages just so any popularity of the coin would make them rich. The incentive to be an early adopter definitely applies (as well as an incentive to be the creator that gets a mining head-start), and that aspect of Ponzi schemes is relevant for most shitcoins.

Whether it's a hype bubble or an explicit Ponzi scheme, Gravel is right about the need for more people to buy in all the time to fuel the speculation. It's a bit misleading, as Bitcoin wasn't designed to be a speculative bubble from its outset. It's still important to describe Bitcoin by what it has become: a devastating international pump-and-dump scheme with a benign beginning.