That definition of "otaku" is outdated. Although I love Karl Taro Greenfeld's writing ("Speed Tribes" was a great book about Japanese subcultures), that article is at least 10 years old.

Otaku now are considered to be especially obsessive fanboys and girls, who geek out on a particular genre or subgenre. (Think of the Trekkies here who learn to speak Klingon -- MAJOR Trek-otaku)

Since I'm lazy today, Wikipedia puts it nicely this way:

"In modern Japanese slang, an otaku refers to an overtly obsessive fan of any one particular theme, topic, or hobby. Common uses are anime otaku (one who sometimes enjoys many days of excessive anime watching with no rest) and manga otaku (a fan of Japanese graphic novels), pasokon otaku (personal computer geeks), gēmu otaku (playing video games), and otaku that are extreme fans of idols, heavily promoted singing girls. There are also tetsudō otaku or denshamania (metrophiles) or gunji otaku (military geeks)."

Atom's definitely otaku: I'm betting he geeks out on kaiju, hentai anime (especially the tentacle and lolicon subgenres), and pinku eiga.

And if you don't know what those mean -- LOOK 'EM UP! -_-"

i didn't actually read their def...but i can tell you it's way off.

it means (anime) freak...most of whom tend to be nerds, but not automatically in a bad way at all...

cosplayers are usually otaku.