Is it acceptable to use wikipedia articles as reference sources for a university essay?

I've heard some people say it's not as wikipedia can be edited by anyone and yes, while true so too can anyone write an article and throw it up on the net. On the university course I'm doing we have an online environment with various course material which has been placed there by the lecturer and some of that study material are actually wikipedia articles, so a lecturer really couldn't turn around and say wikipedia isn't a suitable reference source when they themselves use wikipedia as course material. What d'ya think? Thanks.