Cryptocurrencies have quickly become a hot investment that is gaining mainstream adoption. Markets for digital currencies such as Bitcoin (BTC -0.56%) were virtually unheard of in 2012, but it has since grown into a massive industry. A graphic showing different cryptocurrency coins as plants sprouting from the ground with an arrow pointing upward. Image source: The Motley Fool The cryptocurrency sector reached a peak market value of $3 trillion in fall 2021. The sudden surge in value and rapi...