DS attends a very large university.
He explained the use of "they" one day last summer when he was home. He referred to a girl he knew in high school as "they." Of course he had to explain all of it to me, and it took a while. It is not simple. I knew her too, and I still talk about her as "she." She doesn't come up in conversation very often, but I know this is something I'll have to deal with from now on.
It's amazing what the professors in science classes there teach - gender neutrality, fairness/equality, and politics. Let's hope they get some science in there too! 
ETA: DH and I were out to dinner one night. Our server had a unisex name, short hair and glasses. DH was not used to anything like this. He didn't know whether to say "he" or "she," so he didn't talk! I just kept using the name, telling another server, "Alex said Alex would get it for us." I didn't know any other way to do it.