Ask anybody involved in academia and they will tell you without hesitation that Wikipedia is not a valid source to reference in an academic article.
While I understand that SE is much like Wikipedia (in that it is user editable), I don't feel that Wikipedia should be allowed as a valid reference for answers.
Sure, we can't stop users from posting answers that reference the 'pedia, but if we stop new users from quoting from it during their "First Post" review, hopefully we can encourage a more academic stance within the community.
I'm not against a question citing Wikipedia if need be as it's a question and needs to be answered; if Wiki is the only source they can find it's our duty to help them out.
I think this is something that needs discussing while in beta so we are clear when the site goes live.