There are goddamn lawyers watching this goddamned fandom, okay, and they don't give a shit if it's "for a good cause". We have no right to sell our fic or arguably even talk about it in monetary terms, okay? Most of you are writers, so why don't you make like writers and choose your words more carefully, for fuck's sake?
Sure, it's cumbersome to say "person X donated $Y to Charity Z in exchange for me taking the time to write this fic" -- I mean, why bother, when you can say "my fic sold for $Y" or "person X bought my fic for $Y"? You're not the only one in this fandom, that's why, and your careless, self-serving substitutions may potentially land all of us in serious trouble.
What's most galling is that if this shit does catch the attention of JKR's legal beagles and brings a new flurry of C&D notices on our heads*, everyone will predictably point at the people who organise the charity fic/art drives -- when it's absolutely NOT their fault.
*(no one remembers the last time that happened, do they? I see no other explanation for this bullshit. I wasn't even in the HP fandom when that happened, but see, that's why God made Google and spoke the immortal words "lurk moar")