Yet there is a real downside to bitcoin and other cryptocurrencies. It's almost impossible to quantify, but you can look at some red flags and exercise some caution.

-- Bitcoin can still be hacked and stolen. Like any other cybersecurity issue, every dark hacker in the world is trying to steal bitcoins. It's a 24/7 enterprise.

Think about it. If you have the technical chops, it's much easier to steal bitcoin than money in a bank. You don't need a gun, getaway car or have to face armed security guards or cameras. All you really need is a computer.