Even during my masters I have always felt that it was not done or at least questionable to cite wikipedia. However, wikipedia is often an excellent source for a first read on a new topic. The next step should then be to read wikipedia's sources, and slowly expand your view on the subject.

However, sometimes it happens that you read first about a topic on wikipedia, and worked something out on the information you found there, before you had time to consult wikipedia's sources. In this case you definitely should cite wikipedia.