If a site hot links to an image on my site, isn't that essentially a vote for content on my site? Is there any SEO research on whether google or other search engines give any kind of PR boost to my site? The other site in this case is a myspace blog that didn't have permission to hot link.
Hmm, nice question... Allthough i myself usually don't mind hotlinking, i can understand people who dislike that, do i gather that you don't like it? I don't know how much PR this myspace blog can share anyways, and if it will affect your rankings... It won't hurt, but if you'll profit from it.. i dunnow... What you could do: add a watermark to the hotlinked images with your URL in it, might get you some real traffic
The original Larry Page patent that dealt with PageRank stated: This is no different from the more common explanation which is stated in terms of 'page importance' and 'votes for pages'. However, I find that it makes the PageRank concept somewhat easier to understand. So, returning to the original question as to whether someone hot linking to an image on your site isn't voting for your site, I'd say definitely not in PageRank terms. Someone simply running an image on their web page from your server does not provide a 'followable' link from their page to your site, so it cannot alter the probability of them arriving at your page and so cannot influence your or their PageRank according the original PageRank model. It is probably best not to think of the src attribute of an image as a link at all, but rather as a file location reference.
I agree with all responses. I am not seeing much traffic from the image, so I'm not worried about it right now. I am not blocking hotlinks now. I believe that an image link might well be considered as a vote for a site -- I agree that it may not be given by the search engines of today. I would suggest that it should be a factor since that user liked my image enough to use it. Perhaps we can get this idea to the search engine developers.
One thing that I have started doing is emailing peope who have hotlinked my images and said "credit the picture with a link to my site or remove it". This way you can at least end up with a few link to your site if you're lucky.