Bob's friend sounds like classic Asperger's Syndrome. I love to talk about radio and music charts, but unlike many with the same disorder, I have a sense of when to shut up. As Nat said, these type of syndromes are spectrum disorders which means those afflicted can certainly vary to a large degree. I've always thought my case was somewhat mild.
Many people with this syndrome also suffer from sensory disorders. I may have a mild case of that as well. Nat knows from another board that I can't stand to be without a shirt. He always thought it was because of uptight parents (who were very modest) but I actually think it might be related to Asperger's. Right now I'm sitting at home by myself relaxing in shorts and a t-shirt, barefoot, but I could not get relaxed if I was also shirtless even though I'm by myself.
Whatever degree of Asperger's someone has, 2 things are almost always true: intense interest and knowledge in one subject and lack of normal social skills. I've had to teach myself to try and overcome the social part due to business reasons, but it is a big struggle. I had to go to a dinner party the other night and I HATED every minute even though these were not strangers. I just can't do small talk.