The proper use of Wikipedia
It is routine practice for college professors to tell their students not to cite Wikipedia in their assignments for class. There's a good reason for this: Wikipedia is an open-source encyclopedia that anyone can edit. That's why it's prone to misinformation - such as when Rush Limbaugh was pronounced dead a couple years ago and when Barack Obama was listed as a Muslim. There is not a filter to pre-scan edits for accuracy.
(That said, Wikipedia does not make mistakes in the same way that the HeraldTimesOnline.com comments section does not make mistakes. The users of both websites make mistakes. It is a critical difference - Wikipedia is not the Encyclopedia Britannica.)
Now, in fairness to Wikipedia, there is an active community of users that fact-check each other to make sure information is as accurate as possible. For casually looking things up, it's perfectly fine and I use it often. However, it's not appropriate for a lot of cases - such as academic coursework, as I mentioned above.
And like or not, no matter how good Wikipedia is and how much it has been improved, there is the issue of public perception. Many people are simply going to dismiss Wikipedia, so people who wish to write a convincing opinion piece for public consumption (such as a letter to the editor) won't use it.
The best way to use Wikipedia for those cases where it isn't appropriate (such as academic coursework, journalism and opinion writing) is to look at the sources listed at the bottom of the article and then cite those sources directly. After all, Wikipedia's guidelines require that claims of fact made on Wikipedia have a citation from a reliable source. Then there's no issue of credibility or public perception.