According to the Fortune Magazine article This Billionaire Just Called Bitcoin a 'Pyramid Scheme', Howard Marks said:
In my view, digital currencies are nothing but an unfounded fad (or perhaps even a pyramid scheme), based on a willingness to ascribe value to something that has little or none beyond what people will pay for it.
See also the Washington Post article Bitcoin isn’t the future of money — it’s either a Ponzi scheme or a pyramid scheme.
Wells Fargo's CEO had this to say:
Bitcoin is not only a "pyramid scheme," but it "makes no sense," Kovacevich told CNBC in a Tuesday interview. But to call bitcoin a fraud would be an error, he said, since "everyone knows what is going on" and nothing fraudulent is occurring. Bitcoin, in Kovacevich's view, is merely a "pyramid scheme" because bitcoin investors are, at the core, "betting that someone is going to buy it" at a higher price.
And from Jamie Dimon, CEO of JP Morgan:
In October, Dimon said at some point global governments will step in and crush cryptocurrencies if they ever get to the point where they pose a true threat to government-backed currencies. Dimon called investors who buy cryptocurrencies “stupid,” but acknowledged the price of bitcoin could get to $100,000 per coin before it ultimately collapses.
Is bitcoin a pyramid scheme?