I tend to relate cryptocurrencies to common electronic currencies like Air Miles or Frequent Flyer Points.

The folks I've talked to have no problem with Air Miles and how you can collect them by making purchases using the card.

For the true beginners, they don't need to understand the intricacies of blockchain and hash rates. They simply need to know that if they do something, they have the possibility of gaining a tiny bit of electronic currency. After a while, it may add up to something.

I usually remind them that they've never made a penny on Facebook or the Facebook games. ;-P