It's interesting isn't it?
I'm a nerd, my brother isn't.
I read sites like the Escapist and repair machines for a living (computers), I have a weekly game of D&D at a local gaming club, I keep up on the latest information about games coming out, the latest about books, tv shows, and movies I like, the newest tech coming out (computers).
My brother reads sites like ESPN and repairs machines for a living (cars), he plays a weekly game of Fantasy Footy at a local bar, he keeps up on the latest information about his favourite sports, who is up and coming, who is retiring, who might be traded, the weather conditions, past performances (ugg he bugged me write him a spreadsheet for his stats), all the while keeping up on the latest tech coming out (cars).
So why am I considered a Nerd and he isn't? I'm use to it, I embraced being a nerd and stopped being angry about it 15 years ago, but if you called my brother a nerd he'd likely punch you in the face.