Bit late, but I stumbled across DeepDyve, which provides rental access to scientific papers for as little as $0.99. The pitch to publishers is: Renting a paper means you get to read it online, but you can't print or download it, and access is time limited (unless you purchase the article outright). You can also purchase monthly plans (think Spotify for papers). It's an interesting model, and the interface looks nice.

Continuing on this theme of embedded metadata, this is one reason why DNA barcodingis so appealing. A DNA barcode is rather like embedded metadata -- once we extract it we can look up the sequence and determine the organism's identity (or, at least whether we've seen it before). It's very like identifying a CD based on a hash computed from the track lengths.