~~ crackfic vs. AU: taste the rainbow

I feel my quest to be a total mindless squeeing fangirl keeps getting derailed. But only some of the time-- which I think can be narrowed down to whenever I'm not reading manga. You know, those people who say 'it rots your brain' as if that's a bad thing are just kind of uptight, aren't they :>

Anyway. Not least because I'm writing a couple myself will I or nill I (mostly nill I, but what're'ya gonna do), I've been thinking about AUs and their definitions.
    This got sparked by winsome1's post about a negative review to her fanfic, which basically has Harry run away from home after 5th year and stay in a whorehouse, after which he became a stereotypical gay boi, called people 'sweetheart' & couldn't resist Draco's manly charms.

    Now, the reviewer and the author seemed to actually agree that this set-up is implausible-- the difference being that the author said she never intended to write a 'plausible extension of canon', and wondered whether she should've warned for that. Of course, all the comments to the entry reassure her that no, warnings are for uptight losers (though not in so many words). And in a sense they are, 'cause people should really be clever enough to figure out when something is a crackfic.
    Heavy mention of rentboys, Veelas, soul-bonds, most Medieval torture devices, and possibly sparkly green hair and purple eyes should all be dead giveaways. Most Harry/Draco fluff should probably also fall into that category (then again, definitions of fluff will differ: mine involves most PWP non-hatesex smut, fic with free usage of given names, weeping!Draco and possibly kittens). ^^;; But honestly I see 'crackfic' as using any trope, scenario or genre (like fluff or hurt/comfort) and taking it far beyond the realm of canon plausibility (unless someone out there really wants to argue something like, 'but why couldn't have Draco been sexually abused and then become Harry's soulmate-of-DESTINY').

( Geeky definitional quibbling ahead. )