An amusing WWW 2008 poster by Joshua Blumenstock, "Size Matters: Word Count as a Measure of Quality on Wikipedia" (PDF) found that a very simple measure of "quality" of article on Wikipedia, the number of words in the article, performed nearly as well as much more complicated classifiers.
Word count with a simple threshold achieved 96.5% accuracy in the classification task. The other more complicated techniques ranged from 81-98% accuracy.
Joshua is careful in the paper to not "exaggerate the importance of this metric", but I believe there is a lesson here: Try the simple things first. It can often be surprising how well something simple works.