I wish there was some way of telling if a site would allow remote linking or not. If I find an image on google and go to the site to look at it and get the address, it is then in my cache so it shows up for me when I do a preview even if it wouldn't for the average person.
Maybe someone can do a plugin for Firefox which fakes the browser request to make it look like it is a local request for an image instead of a remote link.
