Maybe a
p2pMarket based on it's own blockchain ? You will be the first to make one if you like the idea
Hmm, that actually sounds quite interesting. However I'm wondering what you mean exactly with basing it on it's own blockchain. Wouldn't a simple bitcoin-version of Ebay based on a web of trust (including user ratings) work?
Exactly, the programmer would use the blockchain database style for all back-end storage of information (namecoin for example) He can use standard JSON or anything he likes.
The heavy lifting would be done by the GUI by sorting and filtering of all kinds of info from the local blockchain (
data example)
Can be a perfect copy of the actual
OTC market with the only difference it's decentralized

You can build lot of stuff around a working model of that... digital ID creation assisted by the software, public or private PGP chat, fees for every listing sent to the network to incentive ppl "mine the blockchain", you name it...