In defense of beards: first, bearded economists are if anything over-represented among Nobel winners. Second, although a nutty professor/homeless guy beard is probably unprofessional for industry, it might very well increase effectiveness in teaching. Combined with well-timed crazy eyes, the homeless guy beard can strike just the right amount to fear into undergrads' hearts. And when you're trying to teach a room full of hung over nineteen year olds how to calculate price elasticity at 8am on a Friday, fear is pretty much all you've got.
I have had a professor with a beard and crazy eyes! He began each lecture with an enthusiastic, if not slightly demented, "good afternoon scholars!!!" It definitely catches you off guard the first few times. He ended up being my favorite professor.