All currency is just a statement of trust. Gold and the like are trust that other people will want gold and gold will remain hard to come by (note that gold could be devalued massively if it could be efficiently extracted from asteroids/seawater/Earths core with future technology). Fiat currencies are a statement of trust in a government, which is made of a fairly small largely self selecting group of people therefore pretty corruptable so this trust should not be absolute. Crypto-currencies are are statement of trust in an algorithm and (for proof of work systems at least) the idea that with a large enough number of users each user will be 'forced' to act honestly (everyone else loses if one person cheats so everone is out to stop anyone else cheating, it's game theory in practice), of course you point out there are flaws with these assumptions-and there certainly are. The crypto world knows this- it's the search of better solutions that is the truely exciting element of crypto currencies at the moment, they're still in alpha testing.