I am currently administrator of a Warez forum, and we use download links from different file hosts. See, we post these links because that if we were to get caught upload ing these movie/game/anything files to our Forum Server, legal issues will follow. See, the site itself would not get in trouble, since we provide links to where the download is held, and our site itself does not hold the download.
Now getting to my point. If we were to allow download links like that, our precious hack forum would not get sued. There are many virus scans for links out there, i'll just have to find them, and we'll have to work on making this mandatory, should my suggestion be approved... for lack of a better word.