The Wikipedia is a wonderful source of information. It has a self correcting mechanism that allows a tremendous body of knowledge to be amazingly accurate. But the quality of the Wikipedia varies depending on the expertise of the authors and editors, and sometimes vandals can insert totally erroneous things for mischief, and sometimes things are changed for purely political reasons.
One very useful, but little known, feature of the Wikipedia is the History tab that lets you browse through past changes to the pages.
Today while I was browsing edits, researching possible political propaganda inserted by someone promoting one of the conspiracy theories about Barack Obama, I ran across an example of some false information in the Wikipedia that was there just for a moment.
In the article on Sun Yat-Sen, the first president of the Republic of China, I found the following:
Sun Yat-sen was born on [[12 November]] [], to a cantonese peon peasant family in the village of [[Cuiheng]], [[Zhongshan|Xiangshan]] county , [[Guangzhou]] prefecture, [[Guangdong]] province (26 km or 16 miles north of [[Macau]]). The chinese of the middle Yangtze are the real chinese, cantonese are freak mutants from MARS! When he died in 1925, the name of Xiangshan was changed to Zhongshan, Sun’s Japanese name when he was living in Japan.
Wikipedia: Sun Yat-Sen History
It is a particularly useful technique, when looking at controversial topics, to view the Discussion and the History pages on the Wikipedia articles to detect changes made recently to support a particular political view.
Here is another example of Sun Yat-Sen Wikipedia vandalism.
and here is an example of another bit of vandalism.