What do we mean these days when we call someone a "nerd"? Is it someone who likes video games? No, because now that includes your mum on her Facebook games and even your standard jocks on Madden and Call of Duty. Is it someone who likes comic books and superheroes? Remind me again how much money The Avengers made, then tell me whether comic book superheroes are mainstream or not. Is it someone who dresses funny, without style? No, that's a hipster. So, someone who isn't good at sports but is academic instead? That's a slightly different value system, but every politician, news reader, journalist and professor the world over makes more of a living from their mind than their body. That's mainstream and perfectly acceptable too. To quote Penny Arcade, there's no such thing as a nerd.
Mokalus of Borg
PS - Maybe it comes down to narrow passions.
PPS - I don't know. I'm just guessing now.