I've had the ponzi argument via public forum on multiple occasions. It comes down to people not knowing what a ponzi scheme is. Early adopters profiting more than late comers =/= ponzi scheme.
Yeah, it would be the similar to suggesting that Apple is running a ponzi scheme since those who purchased stock when the company was circling the toilet in the 2001 profited when the stock when to over $400/share. Ponzi and scam have to be the most overused words by financially ignorant internet trolls.