Fake geeks and Otakus are EVERYWHERE!! And I mean everywhere! But... how do you sort out... the liars?
No, it's not the cruciatus curse.
You ask them questions! If someone claims to be a geek or an Otaku about something, but can't answer the world's SIMPLIST questions about it, then they are clearly a fake!
(Like, if you ask someone who Jean Havoc is-and they answer with 'a character from Elfen Lied'
;-p)