"Normal" users get kind of annoyed by intermediary pages. They want to get to their proxies and then to MySpace (etc...) as quickly as possible. There are, unfortunately, other attacks against that method. Yes, we have that anti-spam measure implemented also. That's a pretty cool idea!
You could set the meta redirect to 1 second, that would not be long enough to annoy anyone I think but long enough for the framebuster JS to work its magic. Yes it is, in fact many sites use this method now to protect their files. If you go to youtube for example with flash blocker installed and wait about 3 minutes or so then click the .swf to load, it will give an error. This is because your sessionkey expired and the Youtube server is actually throwing you a 403 forbidden error if you check the http headers. The files there are loaded in this formate youtube.com/get_video?video_id=My0FyN72Phc&t=vjVQa1PpcFMYw9rimTxDRmtrwSNk-Cy_IWhB53fZjzQ=&el=detailpage&ps=&fmt=34 The &t is the session key. I'm not sure how it works Will, but the key is probaly generated from a PHP session and mapped to your IP or something. If you noticed Glype makes use of this sessionkey, with Unique urls (If enabled). After you leave the site, the links will be dead. This prevents hotlinking abuse period. Maby take alook over the glype code how it implements it.