After having read the HEX "layman's guide," there's a couple different ways to approach defining what HEX is:

1. HEX is not a Ponzi scheme as it will always pay out what the terms of staking dictate (whereas Ponzis always eventually collapse and stop paying). It's also not a MLM per se as it only has 1 level of referrals.

2. HEX is a Ponzi scheme because it requires an ever-increasing influx of new users in order to keep the price growing, or just stable. Those already in will constantly try to recruit new holders to prop the price up.

If you choose to go with #2, well then you have to account for the fact that most (if not all) cryptocurrencies are at least somewhat inflationary and require word-of-mouth in order to attract new investors (aka, people to sell your bags to).

The difference between HEX and most other cryptos is that HEX does not purport to do anything other than go up in value. It has no plans to be a means of currency; after all, Ethereum already does that, and if people want a currency they would just use ETH as they need it to transact HEX (an ETH token) anyway.

Final assessment: HEX is a worthless shit token led by a douchebag, but it is not a scam.