I should point out that Word of Mouth and referrals is what helped PayPal get 7 to 10% daily growth during the early days of Paypal.

In Elon Musk's own words "Yeah. Well, we started off first by offering people $20 if they opened an account. And $20 if they referred anyone. And then we dropped it to $10. And we dropped it to $5. As the network got bigger and bigger, the value of the network itself exceeded any sort of carrot that we could offer."

I think cryptocurrencies also should follow a similar strategy until they get enough visibility and adoption. We can't say this for Bitcoin and Ether likes. But at-least the new coins which are failing due to lack of marketing and their anonymity could try this.