At least during the dot-com era you could speculate that one day these companies would turn a profit, which they would translate into dividends, so you could speculate on an intrinsic value down the road. Bitcoin doesn't even purport to pay dividends. Owning a Bitcoin will not pay you a dividend, unlike a share in a company that may one day profit. I guess what I'm saying is, what is underneath Bitcoin that is valuable and that therefore justifies the price?
On March 19th, 2018. See this statement in context.