"Professor of Brooding" - a Teacher's Take on Professor Snape

MSNBC has an amusing essay on the classroom stylings, behaviour and attitude of Professor Snape. Contributor Mary Beth Ellis writes that he is

a man who dressed for occult success; you can’t swing an appointment as an instructor in Defence Against Dark Arts when you’re trolling the halls in a teal cardigan and loafers.
This is not to say that Snape doesn’t care about his students' education, in a sarcastic, uncheerful, I-hate-you fashion. He'll even save a life here and there, as long as you don’t try to hug him or talk to him or walk within a five-mile radius of him afterwards.
But why all the hatin', Snape? Fan speculation includes the usual psychological analysis: Bad childhood, massive crush on Harry Potter's mother, massive hatred for Harry Potter,s father, wound up with Brett Favre as his starting quarterback in the Hogwarts office fantasy league.