I was on the fanfiction site today and read this guy's theory, which was quitew eerie given I've just this week finished a re-read of Prisoner of Azkaban. Even before I read the page, there's this "Love Potion" line in it from Mrs Weasley that really jumped out at me too, telling Ginny (and Hermione) about this love potion she made as a girl. Given how immoral and even dangerous we're later told love potions are, it seems a very irresponsible thing for a middle aged mother to be gossiping with two young girls (one of whom is her daughter). This guy has a theory (which is creepily backed up by the evidence in the book) that someone had dosed both Harry and Hermione in the 6th book to go for Ginny and Ron respectively (an awful lot of people, myself included, find both relationships painfully unconvincing and even downright weird). He notes Ginny as the obvious suspect (given she's been obsessed with Harry since she was like 9 (!), yet he never looks at her twice beforehand and then it just seems to happen out of nowehre)
The theory is creepily convincing, espcially as he notes, when Rowling does have a habit of putting in seemingly throwaway lines in the earlier books that later turn out to have major significance. Though I'd say Ginny is not the only suspect. Mrs Weasley always made it only too clear how much she wanted Harry and Hermione in the family, and regarded them as such. Then there's Ron. I certainly wouldn't put it past him to be stupid enough to use one on Hermione and while using one to make Harry lust for his little sister seems a tad unlikely, on the other hand... we KNOW how insecure and jealous he is of Harry and Hermione's relationship, and given he knows how Ginny feels, if he wanted to shove Harry toward someone else...
Just sayin'. He's pretty much convinced me though, esp with all the other irrational behavior exhibited by Harry and Hermione in HBP (attacking Ron with birds??!!? Does that sound like Hermione, or someone under the influence of an obsessive love spell?).(Though almost all of this was cut out in the film).
Either that, or Rowling had just completely lost the plot by then.