lucy24 - 8:06 am on May 25, 2012 (gmt 0)

I think part of the challenge is that many sites serve their images from a different domain - sometimes extremely different - to allow more parallel http calls. So Google can't assume that situation is always a hotlink.

Uhm, that was my point. If the images all live at a single domain-- even if it happens to be different from the page's domain-- there can be reasonable explanations. But when every single image comes from a different place, that ought to set off alarms. Hotlinkers rarely stop at just one.