Preventing file sharing should be relatively simple: Just encode the purchasers name, verified credit card information, address, and other sensitive data in the file, and have a portion of this data displayed during playtime (eg. 'owned by: Thumbs Murphy' in the song info/title). With a little hash-action (possibly some public-private scheme) over the entire file, modification of this data would not be trivial.

Additionally you can watermark the file in the content itself with this data. So unnoticeable audio anomalies, video artifacts, in-game textures that will be automatically constructed to reveal this data *and* the necessary keys to properly decoding the data.

I'm not saying that this couldn't be circumvented, but at the very least it acts as a significant impetus to sharing for the general public, while still allowing freedom to move the files around/copy as they choose. Hey, if you own it legally, what's the harm in having your name on it?

Weather or not the public would go for this remains to be seen. I know I probably wouldn't...... Ironic.....

Of course, preventing copying of the source content is another story altogether. And release groups would likely still be able to easily release tons of material if only a re-encode of content output. However, the watermark scheme, if well implemented, may deter this from happening on as large a scale as current.