You have a full-on meltdown when you come home to find your CD shelf has been moved.
You argue with people by remaining completely dispassionate and pointing out the inconsistencies in their thinking, while watching them get increasingly annoyed and angry, all the while wondering what all the fuss is about.
You are almost completely immune to mainstream advertising. (Ads for computers, music gear, non-consumer electronics, etc., don't count, because those are ofter based around specs and information.)
You routinely walk into things because you're staring at the floor.
You have trouble recognizing faces, but you know the eye color of everyone in the room, which is odd because you don't look them in the eye when talking to them.
You don't pay attention to celebrities, but you know the biography of every member of the cast of the last film you watched, because you watched the credits, and having basically committed them to memory, you look them all up on Wikipedia, because of course you look up everything on Wikipedia.
At some point in your mid-twenties, you realized that most people drink at parties, some of which you would be expected to attend, and you realized that learning something about wine, beer, and cocktails would give you something to talk about when stuck at a party. ("Oh, I see you're drinking a Shiraz. Did you know that style of wine was originally made in Iran?")
You celebrated your 32nd birthday as your Goldenberg Variations birthday, and your 34th as your Fibonacci birthday.
You had to quit going grocery shopping for awhile, because you found yourself analyzing the Muzak.