> The simplest thing would be to extend the "accredited investor" standard, such that anybody who wants to play the digital ponies either needs to be rich enough to afford the losses or prove sufficient sophistication that they really know what they're doing.
I think this is already more or less the case. The SEC recently updated the accredited investor standard to include not just means testing, but alternate sophistication tests like Series 7/63/etc, CFA iirc. I’m not sure how/if they fully enforce it or not, but they do to at least some extent, which is why FTX, Binance and others run two versions of their services, a US-based one and an international one.