"This seems like it would have a serious early-adopter problem, in that it needs a pretty large network of people that somewhat know each other in order for thi

"This seems like it would have a serious early-adopter problem, in that it needs a pretty large network of people that somewhat know each other in order for things to work." It's a classic, textbook example of the network effect: the more people use the service, the greater the value for each user. If a network of early-adopters were established and enough momentum were gained, it could perhaps work. "I also don't see what the incentive is for someone to join." Some might have an incentive to join. Some die-hard anarcho-capitalists would perhaps join for a matter of ideology. Others, like money launderers, would perhaps join so that they would not leave a paper trail. "A way to transfer money electronically between people who know each other, across trans-national boundaries with no government tracking of the amounts in or out...what could go wrong, from the perspective of the Feds?" Ripple looks like a P2P approach to the hawala system, and if the Feds are targetting the hawala system, they would doubtlessly target Ripple. However, cryptography might provide plausible deniability. I don't know because I am no expert on financial crypto and the like. Last but not least: I personally find this an interesting concept, not much else. A rigorous mathematical analysis would be required to show that the system does work. One would have to study the robustness of the system to malicious nodes. Let us see: graph theory, game theory, mechanism design, cryptography, law, etc. There's food for thought here for many years of research...