Wikipedia is amazing. I love it as a generally reliable source of a tremendous amount of information. Sometimes it may not go as in depth as I might desire. Sometimes it may err on the side of being too even-handed. Generally, though, it is fantastic.
Several times I've been in online discussions, cited info in Wikipedia, and been told that I need to cite other references because Wikipedia is unreliable (since anyone can edit it). Ironically, this objection usually comes from people who are not backing up their claims with any citations at all.
Anyway, that arguments sounds good on the surface but fundamentally misunderstands the strength of Wikipedia.
Though Wikipedia is (of course) inferior to primary sources, it is of similar quality to an encyclopedia. The fact that anyone can edit it is actually a strength. Yes, spurious info can creep in (especially for a subject that few people are paying attention to), but there is also an extraordinary community of people who monitor the content, correct errors, make sure the info is balanced and even-handed, etc. This is possible because a large and robust community is in control instead of a small number of information gatekeepers.
In fact, a study by the scientific journal Nature a few years back showed that errors occur in Wikipedia at a rate that is only slightly higher than the Encyclopedia Britannica (link, there are also links there to EB's objections and Nature's response to them).
Wikipedia is not perfect (what source of similar breadth and accessibility is?), but it is certainly trustworthy enough to be useful for silly online discussions.