Then you could say that all casino games are sc.am as well, what is your definition of a sc.am??
If the ponzi owner doesn't run away with the money and if he doesn't advertise the ponzi as a safe investment it looks like a gambling game to me
Are you serious? Casino games can be provably fair. You don't go in expecting to win. It's a chance.
With a ponzi, someone is guaranteed to be ripped off, even if there is only one person! As soon as the first person has deposited, the ponzi can no longer pay everything that is owed, and requires new deposits to pay old debts.