I find myself leaning towards bitcoin. Some one mentioned in one of the earlier comments that it is proof of work. And I believe that you ‘really’ dont need countries to back your currencies.(right now we do, but bitcoin can change that). Anything which people perceive has a value, can be used as a legitimate currency. The most important thing here to understand is that it will eliminate.. Or at least reduce the number of middle men…and this will keep bringing in more users… Thus a valid currency if enough people start believing in it… But for that to happen it might take long.. Plus the unwillingness of banks to participate..who knows if it will survive or not, but it has prospects .

http://www.economist.com/news/finance-and-economics/21599054-how-crypto-currency-could-become-internet-money-hidden-flipside