Harmy said:

So, such a file could basically make sure, that whoever downloads will first need to own the BD? That sound like a good idea, except that would mean that the person would have to have a BD drive in their computer and it would also probably take ages for a slower computer to do it.

Yep, but there's no guarantee that their rip will be bit-for-bit identical to yours since some BD ripping programs screw with the stream headers, etc. You'd have to post which program you used as well as a checksum for your file.

Also, it's likely that the binary diff would be bigger than just distributing the file outright. Binary diff-and-patch schemes really only make sense when there are very few changes to the original file.