Maybe I mis-understood your orginal post. I thought it was just about keeping google from hot linking your images. Maybe I am missing it or did'nt read the posts well enough. From what I read, your just blocking google or yahoo from loading the real image on their page or results. instead your giving them a different image, your not redirecting them. Guess I dont understand how it's cloaking, maybe just me..
I was saying the problem of hot linking has been around for a long time, I cant see the SE's penalizing any one for trying to stop it from happening to their site(s). Or having a system in place to try and prevent it.
ronnie