I have critiqued the wiki revolution (see posts in 2005 and in 2006) because I worried about the garbage-in garbage-out problem. That is, how can consumers of wikized information know whether the information is valid? Previously, the knowledge culture has relied on editors, peer-reviewers, and publishers to vet information prior to publication.
Wikipedia has come to recognize this problem and is taking steps to lessen it. See their WikiProject Fact and Reference Check webpage. As you browse Wikipedia today, you'll often see pages marked with the warning, "This [entry] does not adequately cite its references or sources. Please help improve this article by adding citations to reliable sources."
This is a great first step. Whether it is enough, we will see. It probably depends on the topic area discussed.
And to be balanced, we must recognize that any influence can tilt content toward one truth or another, whether that influence is an editor or an admonition to cite reliable sources. Therefore, my next recommendation is to formalize alternative interpretations within wiki technology and practice. The wiki interface sometimes formalizes and encourages a "one-truth" paradigm, so where one truth is inadequate, the technology needs to encourage a different sort of mental model, one that allows information consumers to feel the heat, sweat, and uncertainty of the truth-building process.