This is an interesting project.  However p2p trade systems have cost; that is the cost of protecting from double spending.  Either you have a distributed verification network (like bitcoin with the block generation), or you have some sort of trusted centralized user that 'clears' the trades...  (this is normally called a 'clearing house').

If by some miracle you have come up with an algorithm to solve this problem in a distributed p2p manner; it would be wonderful if you could produce a white paper that explains how you propose to solve this doubble spending problem.


I'm working on the Open Transactions project;  this project is building secure (and centralized, but to a server of your choice, in the future we can have a group of federated trusted servers);  the market software executes in a similar mechanism to the Bitcoin scripting.  (through the use of cryptographic market contracts).

I really hope the best for your project, except I'm really scared if it doesn't have the well-thought-out cryptographic foundations (that we are still working on for the Open Transactions project); you will be opening your users up to easy scamming.