Here are some recent articles documenting maliciously wrong Wikipedia information, and even some articles about entirely fictitious entities. In many cases, the wrong information stayed on Wikipedia for years and was cited by other sources. Food for thought if you are using Wikipedia.
I Accidentally Started a Wikipedia Hoax
The 10 Biggest Hoaxes In Wikipedia's First 10 Years
Read About the Infamous Nonexistent Battle That Stayed on Wikipedia for Five Years
Wikipedia's own entry on Wikipedia Hoaxes (yes, we know)