What bitcoin needs in the way of an alternate coinage is a way for any individual to issue their own currency. Such a currency need not require proof of work to secure the block chain...block creation could be left to the issuer and verified based on a digital signature (for that matter, block creation could be managed by several people or entities using secret sharing or multiple signing). This would offer every individual an ability to issue their own cryptographically secure and pseudo-anonymous currency. Their currency could be in the form of an IOU for some other currency (ie. bitcoin, gold, dollars, etc). Building on top of that, a trust network where people decide to what extent they trust another individual's currency could be established. For example, Bill might decide to trust Bob for as much as a $1000 IOU. A routing protocol (akin to BGP) could then be used to find paths through such a network in order to transfer wealth using these privately issued currencies, very much like RipplePay. With a few more pieces added, it's conceivable that you could have a completely decentralized mechanism of exchanging virtually anything for bitcoin.

You could modify the existing Bitcoin client to do that. Call it 'Creditcoin'.

An amount of creditcoin would not be just a number as in Bitcoin, it would be a tuple of a number plus the original address that issued it.

The owner of an address (owner of private key) would be allowed to send an unlimited amount out letting it's own balance go into the negative (thus everyone would also known how much of that creditcoin has been issued).

For example I own the address CL41Guib8ToDmWTHkxgVKtu8rBe4fv1foz and it could hold:

What bitcoin needs in the way of an alternate coinage is a way for any individual to issue their own currency. Such a currency need not require proof of work to secure the block chain...block creation could be left to the issuer and verified based on a digital signature (for that matter, block creation could be managed by several people or entities using secret sharing or multiple signing). This would offer every individual an ability to issue their own cryptographically secure and pseudo-anonymous currency. Their currency could be in the form of an IOU for some other currency (ie. bitcoin, gold, dollars, etc). Building on top of that, a trust network where people decide to what extent they trust another individual's currency could be established. For example, Bill might decide to trust Bob for as much as a $1000 IOU. A routing protocol (akin to BGP) could then be used to find paths through such a network in order to transfer wealth using these privately issued currencies, very much like RipplePay. With a few more pieces added, it's conceivable that you could have a completely decentralized mechanism of exchanging virtually anything for bitcoin.

I believe what you're looking for is a "digital bearer certificate" system. I worked on one a while back called "AEIOU" (an electronic IOU). "Open Transactions" is another DBC system that I've heard mentioned a fair bit lately.

You could modify the existing Bitcoin client to do that. Call it 'Creditcoin'.

An amount of creditcoin would not be just a number as in Bitcoin, it would be a tuple of a number plus the original address that issued it.

The owner of an address (owner of private key) would be allowed to send an unlimited amount out letting it's own balance go into the negative (thus everyone would also known how much of that creditcoin has been issued).

For example I own the address CL41Guib8ToDmWTHkxgVKtu8rBe4fv1foz and it could hold: