There is a populair theory among non-Harry/Ginny-fans that Harry only fell for Ginny as a result of her giving him a love potion. They claim that Harry's feelings developed too suddenly to be natural and that Ginny was obsessed and desperate enough to do this in order to win Harry. They also claim that the prevalence of love potions and potions in general within Harry Potter And The Half-Blood Prince hints that a love potion was used. The theory is particular populair among film-only fans.

The first problem with this theory is that Harry's behaviour doesn't match that of the only other example...