Here's the deal: Wikipedia, according to an article in New Yorker magazine, has the same error rate as the encyclopedia Britannica (which is not perfect). As an instructor I tell my students not to use Wikipedia as a source in any paper because it tells me they are lazy researchers. I tell them to look at some of the source articles for the Wikipedia entry and evaluate whether these are credible.
Now, at one point when I was taking a grad course, I had a prof who said it was OK to yes Wikipedia for basic descriptive surface information (descriptive information, geography information, stats from government sources). I was quite surprised. I have even seen Wikipedia referenced in academic papers (yes.. really) with this type of information. But at least those papers had a whole lot of other research to balance those citations.
In general, I tell students not to use Wikipedia (or other user created sites) in their work, but maybe to give it a glance as a starting spot to get some general info on a topic. There's nothing worse than seeing a paper where all three sources used are Wikipedia articles.