lucy24 - 7:45 am on May 24, 2012 (gmt 0)
I've noticed something analogous: Some of my hotlinks come through google Preview rather than a direct human visit.
You have to conclude that it doesn't set off any major flags when every image on a page is hosted on a different domain. If it counted against them,* the page wouldn't be successful enough to float to the top of Image Search, or get itself previewed. Would it?
I've excluded a lot of directories from Image Search purely because they'll end up as hotlink fodder. Now, if you hotlink to an image that was already hotlinked in the first place...
* It should-- not simply on ethical grounds but because a page loaded down with hotlinks makes for a horrendous user experience. Isn't there a place where google measures page load time?