Well, presumably creating an account will be expensive, otherwise an attacker can just execute a http://en.wikipedia.org/wiki/Sybil_attack http://en.wikipedia.o

Well, presumably creating an account will be expensive, otherwise an attacker can just execute a http://en.wikipedia.org/wiki/Sybil_attack http://en.wikipedia.org/wiki/Sybil_attack Once an account is created, throttling resources is straightforward. If you want, you can allow a person to have one X per Y (time, points, whatever).