It all has to do with the files they try to crawl. lets say someone is looking for Grand theft auto 4 on megaupload, I guess that site will try to look for a GTA4 megaupload and if the file is on wjunction.com I guess they will continue to crawl it, not sure. Filestube had a SUBMIT RSS link but it seems that they removed that function. maybe thats how you could of added sites.