The German version of Wikidepia will implement a simple trust based system to improve quality and combat vandalism according to a CNET article based on an interview with Wikipedia founder Jimmy Wales.
Can German engineering fix Wikipedia?, Daniel Terdiman, 8/23/06
“An experimental feature planned for the German version of Wikipedia could eventually improve the quality of editing for the online encyclopedia and open its front page to public edits for the first time in years.
As always, anyone will be able to make article edits. But it would take someone who has been around Wikipedia for some yet-to-be-determined period of time–and who, therefore, has passed a threshold of trustworthiness–to make the edits live on the public site. If someone vandalizes an article, the edits would not be approved.”
While this scheme is overly simplistic, it’s a good start. I imagine that the policy could evolve and improve rapidly once it is put into place and people try to get around it. There is room to game any trust-based approach, of course, but having a well designed one could help a lot. Wikipedia would be a great testbed for trying out the many ideas for computation trust that researchers are generating (e.g., see Investigations into Trust for Collaborative Information Repositories: A Wikipedia Case Study). Perhaps different segments of Wikipedia, either by language or topic, could use different mechanisms, proving a way to find out which ones work best in practice.