Ponzi schemes are reliant on having someone in charge.
Hmmm, I wonder how long it will be until we have fully automated ponzis, distributing the coins automatically as they come in.
Alright, to change the phrasing (I did use different phrasing in the rest of the post) - it needs a central entity (which could indeed be a bot) in order to distribute coins and run the Ponzi scheme.
BTC doesn't have a central entity to do this, so it's impossible for it to be a Ponzi.
Probably..... *ehem* bitconnect *ehem*
Bitconnect still needed an anonymous group to set it up and run it. A fully automated Ponzi would be created without human intervention.