Did you read the Nature article in December comparing Wikipedia to the Encyclopaedia Britannica? They compare several scientific entries from Wikipedia & Britannica & conclude that "Wikipedia comes close to Britannica in terms of the accuracy of its science entries."
That was in December. A few weeks ago, Nature (to its credit), posted a (pdf) 20-page rebuttal by the Britannica folks which finds faults with the Nature study for several reasons. These include that Nature only looked at partial Britannica entries for some items, for not distinguishing between minor mistakes and major mistakes in counting the total number of errors in each entry, and that Nature didn't review the "free-lance" scientific reviewers' findings. Nature posted its own 2 page rebuttal in which they stand by their original research.
To me, the problems stem from two very different ways of conducting research: the scientific way and the reference-work way. The Britannica folks are mostly concerned that the Nature people ignored the value of the reference work of the Britannica (such as writing style and editing) while the Nature people would probably admit to being more concerned about the number of errors and don’t feel the need to distinguish between major & minor errors.
Also, to quote Paula Berinstein in the March issue of Searcher, "for many subjects, Wikipedia is good enough." I'd add, for everything else, there's Britannica.