Wikipedia can be a perfectly fine resource if it provides a nice quote to support information you already know to be true (i.e. if you are the expert).
Where Wikipedia becomes a problem is if you are using it to, essentially, answer the question.
Question: "Why is it we haven't been able to solve <problem>?
Answer: Well here's what Wikipedia has to say about it: <quote>
That's not a terribly interesting site, nor is it one likely to be seen as a source of expertise.
An all-out moratorium on Wikipedia sources might be overkill (for ancillary support material, it's sometimes "good enough"). But you — as the experts curating this content — should be vetting the questions and answers; use your votes weigh in on content you find particularly insightful or authoritative. That is how you discourage the proliferation of lazy and/or poorly-sourced answers.
As discussed elsewhere — Multiplying possibly 'wrong' information:
First, should we be asking a lot of questions that can be answered by a Wikipedia article at all? If we are, I'm concerned that we're either (a) not asking terribly intriguing questions; the type you encounter in your day to day work, or (b) the answers are not backed by resources and experience of those actually studying or working in this field.
If we're just copying and repeating information found on every other site on the subject, this isn't really making the Internet a better place. I'm not ceding that point; it's just a concern we have to address when we take a closer look this site when we evaluate the private beta.