I agree with most of you. If a girl who wasn't a sister of my chapter happened to be running around campus in my letters I would think she was visiting, or maybe alum I hadn't met or something of the sort. If I found out she wasn't affiliated I would be kinda upset that she was wearing our letters. Like someone else said, we went through a whole process in order to be able to wear those, learned all about them and wear them with pride.
Actually Cloud9 I think that althogh the greek alphabet is free for anyone to wear, the fact that GLO's pick certain letters in a certain order to form the name of an organization does make it legally THEIR letters, the name of the organization is copyrighted.