One difference here is that transaction costs for selling art or diamonds or even shares of stock would be much higher than for selling bitcoin... but I guess you are asking if it makes sense to establish a marketplace for collateralized bitcoin loans, business loans, etc.??
It seems like the hedging function is a separate matter - the value of any currency or collateral might vary over time, and there are established means of hedging against volatility using derivatives.
Has anyone created a market for bitcoin derivatives yet?
But back to my original question
Perhaps here is a clearer way to ask it, given the discussion:
What would stop someone from making agreements to loan each other fungible items (real or virtual items) and earn more of the same in interest?
BTC is such a fungible item - but it hasn't been declared a currency; it's not regulated. Correct?
Also, there are ways of assessing risk between counterparties that do not rely on traditional mechanisms of updating credit reports, etc. There's social networks, transaction history, etc... and per the recent comments, one might also require collateral so the market would support secured as well as unsecured loans.
The distributed nature of P2P lending seems to be a better match for the way BTC works than to require some kind of centralized bank - distribute the risk and let individuals choose their own risk/reward blend.
So why couldn't someone adapt existing P2P lending technology to create a P2P lending system based on bitcoin? You want to loan out your bitcoin and have it gain interest - the system helps you pick the best borrowers; riskier borrowers pay higher rates and will typically default more.
Perhaps you prohibit riskier borrowers based on their credit ratings.
Such a service might be mostly virtual, if it didn't have to deal with onerous regulations - the big issue I see is how would you do Collections to police deadbeats... maybe some kind of alternate consequence could be set up.
I guess it surprises me that although bitcoin is still a tiny market, there hasn't been discussion of this kind of thing because of the large amounts of money involved if an alternate unregulated international credit system could be created with impunity...