Just wanted to drop a note of support for ninjabanker's proposal.

My "holy grail" project is integrating with ninjabanker's project, since it adds fiat currencies without the need for any issuer holding reserves. (Since the reserves are held in cryptocurrency escrow instead.)

In my original "holy grail" post, our solution was to use issuers in combination with colored coins (and we will still probably support that) but ninjabanker's idea goes a step beyond that by eliminating issuers altogether. (So any previous concerns about the legality of "bearer bonds" should be alleviated.)