Citing any encyclopedia or other general reference text as a source is a warning sign, because it means that you haven't done any in-depth research, and/or you'

Citing any encyclopedia or other general reference text as a source is a warning sign, because it means that you haven't done any in-depth research, and/or you're trying to cite sources for information which is considered general knowledge in the field. Wikipedia isn't special in this regard; you're going to get marked down just as much if you cite the Encyclopedia Britannica or a dictionary.