re: Bitcoin is a Ponzi scheme—the Internet’s favorite currency will collapse.

Unlike Social Security, bitcoin really doesn't fit the common definition of a Ponzi scheme at all. Honestly, I'm not really sure why anybody would think that it does.

price bubble that develops from a controlled supply of assets produced or shares distributed =/= Ponzi scheme

I mean, shite, by that logic, every startup company that gave new shares away to mezzanine VC investors would be a "Ponzi scheme" too. That doesn't necessarily mean that the startup in question isn't filled with fraudulent crap or part of a price bubble, but that's completely different from being a Ponzi scheme.