The whole plots of MANY of the HP books/movies is either a Chekhov's Gun, or a straight-out MacGuffin. And the entire SERIES suffers from the Checkhov's Armoury problem of "if anything is named, mentioned, or whatever, it MUST have massive significance, somehow, later."
Yes I've been spending WAY too much time over at TVTropes.org. Damn you xkcd and mentioning it!