Yes. Multiple times. I always found it pretty funny as I'd known they were developing their own right alongside it.

Granted, I think his criticisms are more specific than being about the technology in general.

I think he was more critical of it being penned as some replacement for existing currencies and monetary systems, and the whole use as an investment.

But don't quote me there.

It's like watching a 3-card Monty hustler yelling across the street at the 3 cup and ball guy for being a scam.