What is the general thinking on what the right properties of cryptocurrencies should be to give them nonzero value? (e.g., cheap, low volatility, low transactio

What is the general thinking on what the right properties of cryptocurrencies should be to give them nonzero value? (e.g., cheap, low volatility, low transaction cost (in time and expense to transacting party), reliability of transactions, lack of central authority?) To motivate this, there are many reasons for gold to have become the physical currency of choice, outlined here: http://www.bbc.com/news/magazine-25255957 http://www.bbc.com/news/magazine-25255957 I would imagine that the long-term cryptocurrency will have comparable benefits (whatever those benefits are for cryptocurrencies).