Writing fic so a charity can benefit is not the same as writing fic and demanding that people buy it in ebook form, but to me the principle is the same -- the implication is that I own what I'm offering. But I don't actually own my fic. Boiled down, the transaction is "X writes fic, Y pays for it". To me, it doesn't matter who gets the money. In the end, it's fic for money. JKR can write "fic" of her own world and sell it to the highest bidder. I can't do that with JKR's world; I don't think I have the right, and it's a right without which I'm perfectly content. Writing fic for any money, no matter where the money goes, would make me uncomfortable in my fannish shoes, and that discomfort is not offset by the warm fuzziness of contributing to a good cause.
And because it seems I need to say this every time I state an opinion: this is not to say everyone should feel uncomfortable offering fic for auction. It's just how I feel about it, with no implicit "if you don't feel/think like this, you're a poo-head!". If I wanted to say "everyone who offers fanfic for auction is a poo-head!", that's exactly what I would have said, believe it or not. I've just been thinking about why the idea of signing up for the latest fandom charity event's been making me feel so damned skeevy, and this post explains why. I'm also kind of hoping I'm not alone in feeling this way, which is why I post it here instead of just keeping my thoughts to myself.
All that said, I could certainly offer original fiction, but I doubt anyone would be interested in that. In lieu of offering fic so somebody else can make a donation, I'll donate as much as I can spare to Equality California after I get paid next week. I think they're the ones who'll need it most in the struggle against overturning the new law.