The cryptocurrency's 2018 crash may help cement its place in the bubble record books.

Down 70 percent from its December high after sliding for a fourth straight day on Friday, bitcoin is getting ever-closer to matching the Nasdaq Composite Index's 78 percent peak-to-trough plunge after the U.S. dot-com bubble burst. Hundreds of other virtual coins have all but gone to zero -- following the same path as Pets.com and other red-hot initial public offerings that flamed out in the early 2000s.

While bitcoin has bounced back from bigger losses before, it's far from clear that it can repeat the feat now that much of the world knows about cryptocurrencies and has made up their mind on whether to invest. Bulls point to the Nasdaq's eventual recovery and say institutional investors represent a massive pool of potential cryptocurrency buyers, but regulatory and security concerns have so far kept most big money managers on the sidelines.