I think you're talking about
digital watermarks. It sounds attractive on the surface, but content owners have stated that they don't want to use it, it might be possible to strip, and worst of all the loan scenario is probably not going to work. (I'm no expert on this, so maybe all these issues could be solved, but they sound like a problem for now.)
My main point,though, is that if you allow limited loaning, then a watermark doesn't help anything because one you allow loans to one person, how do you use watermarking to punish for what other people did with something after you gave it away. Hard to hold you responsible, or anyone resonsible for some widespread copying. I think it has to be either technology (e.g. a DRM like eREader or Sony's DRM that allows limited copies, but restricts platforms because of limited implementation and support), or it needs to be morals/legal/convenience based, so people just tend to buy more than they share.
I bet the average music listener with an mp3 collection has a % split of bought and copied music. But if we were all "thieves" bent on copying only, it would be a 90%copied/10%bought split of their copyrighted music. But I think (of the music they really listen to and consider a part of their collection), most people I know have a 80%buy/20%copy sort of split.
The recording industry says they have stolen 20% of the profits. But actually, they have spent hundreds or more likely thousands on music, and I'm pretty sure that if not for mp3's and even sharing, most of them would have bought much less music in total. But it's a tough thing to gauge because it probably also depends on which particular people you run into and have the opportunity to talk to.
Since I've drifted so far that I no longer remember what topic I'm writing about, I will just stop here! Besides, it's much later than I thought it was also.