Very few cases.
But we all know regardless of what laws are in place deep inside we all make personal judgments upon people because of their appearance, and it is wrong.
No it isn't.
People's appearance can say much about them, and the things that it says often are legitimate reasons for making judgements.
I think it is not okay to discriminate when the feature you are judging is beyond the person's ability to control or fix, or if it is something that there is nothing wrong with, but it is one's own prejudices.
For example, judging on skin colour, height, weight (to a certain extent), NATURAL hair colour, etc....wrong.
If someone dyes their hair orange, pierces and tattoos their body, and dresses in a bizarre fashion to get attention, then they take the reaction that comes with it.
I think many have used the "do not judge" scripture in an erroneous way. I would not hire a person who is determined to have an in-your-face attitude, but I would sure be willing to do what I can to help that person to grow and know his or her value and thereby lose the wrong attitude.