I posted the USC rejection via e-mail. Just to clarify: I don't think it's their normal MO and I still got the generic rejection letter in the mail later on, but the DGS wrote to tell me that the professor I had talked about wanting to work with in my SOP has just moved to another university. I thought it was nice of her to let me know, but if it hadn't been for that unusual situation, she probably wouldn't have e-mailed.