The idea of a large, user-contributed encyclopedia is, in principle, a good one. But the implementation of the largest such effort to date, the Wikipedia, is an excellent example of how good ideas can go dreadfully wrong.
Authors of Wikipedia articles are anonymous in many cases, so expertise in the topic is not vetted for accuracy or depth. Worse, for controversial topics and for biographies of living persons, experts are specifically asked not to contribute to the articles. I discovered this when attempting to correct factual errors in the entry page on my name, and for the Institute of Noetic Sciences. I've been asked not to edit these pages, even though I am arguably the expert on me, and an expert on IONS, because it violates Wikipedia's guidelines.
The most persistent editors on Wikipedia, by the way, largely seem to be 20-something students who are riding high on arrogance, because like all kids, they're suffering under the delusion that they know everything. (I recall this state of mind quite clearly from when I was 20-something.) For you young folks out there, believe me, that grandiosity dissolves with life experience. The fact is that nothing is certain, especially what science pretends to know.
Wikipedia's absurd guidelines means that for topics of interest to many people, namely controversies, the articles are guaranteed to be of poor quality. What a ridiculous state of affairs this good idea has come to, one that very effectively does one thing well -- it perpetuates stupidity.