validators in the Ripple system sound like miners in the Bitcoin system.
Not exactly. Validators don't get compensated directly. The XRPs used to pay for transactions are simply destroyed.
the problem i see in Ripple is that validators are not getting paid. no one is going to let their computer cpu time get consumed w/o being paid.
Yes and no. Tor exit nodes don't get paid and yet, there are lots of them. Commercial interests have an incentive to make sure that there are plenty of independent validators, since having them secures the Ripple network.
Joel said new ledgers will need validating every 20 seconds. that's a tremendous amount of work that Ripple will need to get done.
20 seconds if there's no transaction activity. Even more often otherwise!
responsibility will fall on OpenCoin. that is a huge problem right there due to centralization.
Right. We don't want this.
the other problem with validating every 20 sec is that the validator will need his private key available every 20 sec to digitally sign every ledger they deem accurate. sounds to me like this private key needs to be in RAM constantly and will then be publicly exposed undermining security.
A validator doesn't have to connect to the public network. It can sit on a private network, connected to a second rippled instance that is connected to the public network. Validators can publish their validations into the network from any access point, it is not necessary for nodes to be directly connected to a validator to receive the validations.
Ripple seems to ignore the fact that "work" needs to be done and paid for to sustain/build a robust p2p system which is what Bitcoin has.
There's no "law of the universe" that says CPU cycles must spin for useful computation to occur. Bitcoin's proof of work is a novel and brilliant solution to the problem of coin distribution and securing the block chain. But I think it would be naive to assume that it's the only method. Bitcoin showed that it was possible. Inspired by this, expect this wave of cryptocurrency evolution to surprise us with even more unexpected innovations.