Dartmouth College researchers Denise Anthony and Sean W. Smith recently released a technical report of some very interesting research around trustworthy collaboration in an open (and even anonymous) environment: Wikipedia.
What is interesting in this research is the interdisciplinary approach between Sociology and Computer Science, analyzing the social aspects of human behavior and technical security controls within a system. Far too often are those overlapping fields ignored.
Also of interest, Wikipedia's primary security control is the ability to detect and correct security failures, not just prevent them (as so many security controls attempt to do). In an open, collaborative environment, correction is the best option. And since Wikipedia, in true wiki form, keeps every edit submitted by every user (anonymous or not), there is a wealth of information to mine regarding the patterns of (un)trustworthy input and human-scale validation systems.