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I am certain that googlebot considers this as cloacking and images are dropped from search results...
this week I'm actually seeing an increase in image views.
it's allowed to redirect to a watermarked image as long as the image size is the same. If you redirect to a smaller size image but with same scale it won't show up. That's a small signal telling you that it's ok to watermark... otherwise why would they allow same size redirection?
Also I think we waited too long, we should have organized and started redirecting right away to pron content in order to draw attention of people and media.