Is Wikipedia a valid source? In academia, it is not considered a valid source for citing, however; it is a very helpful source for finding generally reliable information. If there are "facts" in Wikipedia that you want to verify, follow the footnotes for the facts (many have them). The footnotes should be primary sources to which you may or may not have access. As a rule of thumb, the more popular the topic the more accurate, because there are more editors and more fact checkers. If you are thinking of using Wikipedia to support an online argument, go for it, and if your opponent has a problem with the source, put the burden of proof on him or her to provide evidence of the encyclopedia's inaccuracy for that entry.
"Everyone is entitled to his own opinion, but not to his own facts." - Daniel Patrick Moynihan