The latest PC Pro has a 5 page spread on Wikipedia, the analysis is very fair. They did WPs ability to tackle deliberate or unintentional misinformation by posting ten small rewordings from an IP address (a single address!), all were corrected within an hour (suprised NOT). Later that week they tried the same thing from different addresses - 10 were correct within an hour and two went unnoticed for a week and they say they were self corrected. The article isn't online yet and I only managed to read it in the bookstore.
It's mentioned in peer review http://en.wikipedia.org/wiki/Wikipedia:External_peer_review
In http://en.wikipedia.org/wiki/Reliability_of_Wikipedia it covers it as such
A further informal assessment by the popular IT magazine "PC Pro", for its 2007 article *Wikipedia Uncovered*[8]http://en.wikipedia.org/wiki/Reliability_of_Wikipedia#_note-uncoveredtested Wikipedia by a similart device to those described above, by introducing 10 errors that "varied between bleeding obvious and deftly subtle" into articles (the researchers later put right the articles it had edited). Labelling the results "impressive" it noted that all but one was noted and fixed within the hour, and that "the Wikipedians tools and know-how were just too much for our team". A second series of another 10 tests, using "far more subtle errors" and additional techniques to conceal their nature, met similar results: "despite our stealth attempts the vast majority ... were discovered remarkably quickly... the ridiculously minor Jesse James error was corrected within a minute and a very slight change to Queen Ann's entry was put right within two minutes." Two of the latter series were not detected. The article concluded that "Wikipedia corrects the vast majority of errors within minutes, but if they're not spotted within the first day the chances ...dwindle as you're then relying on someone to spot the errors while reading the article rather than reviewing the edits."
I don't condone vandalism of this kind, but I think it proves we have a finger on the pulse.
Mike