1337 is sort of a self referential term. It pretty much grew out of the AOL, uh, culture of chatting, etc, as far as I know. 1337 translates to "leet" which translates to elite. In some circles (12 year old wanna be hackers), it is a term of praise. In others (real geeks) it is a term of ridicule. Leet-speak is typing using funny characters, 43nc3. I obviously don't know much of it. You often see it used in online first person shooter games, as in "1 0wn2orD y3r @$$ 1u23R!"

I'm sure someone else could speak to this in a more educated fashion.

I am the Doctor, and THIS... is my SPOON!