So let's say you go to DNG and burn it onto an archival-grade DVD. The DVD gets scratched and you can't open your files. You can spend $4,000 to go to a data recovery center, but they can't always recover everything, if even at all. Lets take another scenerio. If you take your DNG and compress it inside of an archival RAR file. The disk gets scratched and the file becomes corrupt. WinRAR still opens the file and is able to scan it for it's recovery blocks and, with quite a bit of computation, is able to regenerate the DNG for you.