by being centralized.
That's wrong though, centralization is of course a viable method but it is not used in Ripple.If David is right Bitcoin mining is pure nonsense, otherwise vote the answer of Luca!
Mining is nonsense to prevent double spends if consensus really holds... BUT it also (re-)distributes currency units proportionally by hash rate (with some variance due to the random nature of bitcoin's PoW) to any participant.Luca Mattheis also is giving a wrong answer there (which is more of a comment to another answer by the way) - while there is a chance to create tons of validators, they (unlike mining nodes) do not automatically have a say in transaction ordering.
as I know.. 
