Byteball is my bet. It's free if you hold some bitcoin, you just need to sign a message, which encourages wide adoption. You earn interest on your byteball holdings which encourages people to hold. It is completely scalable. It has a completely private method of transacting, which is necessary for dark net adoption. The app will for vendors of anything to easily set up shop.

Byteball could be BIG.

Selling licence for 0.07BTC. This is the Poloniex license for the latest version. It's made me my money back and some but I reckon I can do better by without it. pm'd last 2 replies.