i'm with ian turner.
although i agree that it is giving my bandwidth away and i would consider it an issue if the image/s were called a LOT.
however a hotlink is effectively a citation and that is a good thing. i've never worried too much about what might be a ranking effect right now, but rather what makes my site look good and surely if my images are being hotlinked then that is good - and at some point a search engine will agree with this!
i am hotlinked on countless blogs, i used to get in a fury about this until i realised that many of them gave me a link back too - (not all, but enough for me not to block all hotlinking on principle)