Conventional wisdom says that even if the Bitcoin bubble pops, as it’s been threatening to lately, the damage won’t spill over into the broad stock market. That’s because in dollar terms, the cryptocurrency craze remains tiny compared to, say, the dotcom boom, which led the broader market to a painful crash in 2000. Internet stocks in the late 1990s represented a substantial portion of what was then (and is again) the largest sector of the economy: tech.