The concept of "premined" doesn't really apply to a scheme that has no mining. For currencies that use proof of work to solve the double spend problem, mining i

The concept of "premined" doesn't really apply to a scheme that has no mining. For currencies that use proof of work to solve the double spend problem, mining is a good way to reward miners for providing the useful service of ensuring sufficient proof of work to secure the currency and make it useful before it's possible to do so with transaction fees. Because Ripple has no need for mining, implementing mining to distribute the currency would basically just be paying people to waste electricity. It would make no sense, and an actual valuable asset (electricity) would be destroyed in the process. Bitcoin has demonstrated that mining at a significant profit quickly becomes impossible. So long as mining is particularly profitable, more people will do it. More and more resources compete for ever smaller shares of the pie. Where it secures the currency and the transactions, as it does in Bitcoin, it's an essential service that is worth paying for. Where it is not needed for that purpose, it's a colossal waste of a significant fraction of the value that Bitcoin creates.