Bitcoins are a fad, but that ring is forever.
Remember when a tulip bulb was worth more than a carriage and the horses to pull it? Now a bitcoin is worth more than a car. At least with tulips you got a pretty flower. But Bitcoins have no tangible parts and do not represent anything tangible.
Some Bitcoin proponent is about to say, "Yeah? What is tangible about 'fiat money'?" That's what they call dollars. "Fiat money." To answer the question before it is asked, dollars are backed by a government that runs a country, owns property and has a military.