Wikipedia is a great resource, and I use it everyday. Economics of European integration students have no doubt been running to it in search of different definitions and historical facts. Several student have emailed me today asking if it's OK to reference wikipedia articles in their essays. My answer is a very cautious yes.
Here's why.
Wikipedia should be the first port of call when researching a topic; not the last. So when looking for Trade Creation, use the wikipedia page to find the basic references, and then go there and search further. Don't stop at wikipedia.
So when it is OK to directly reference wikipedia? When you take a direct quote or a diagram from there. Even then, be sparing. Your objective in the essay is to show me you understand some of the nuances of European economic history as they apply to the models we've seen in class and the Lisbon treaty.
You're going to have a hard time convincing me of this if all I see are wikipedia links.
So: use wikipedia, but as the gateway to other, deeper material, not as the final destination.