I took a poll, and the consensus seems to be that changes of this sort should be experiments in new block chains rather than changes to the existing block chain. I'm concerned that new block chains could compete directly with bitcoin (and make bitcoins less valuable), but perhaps there is a way to tightly integrate them with bitcoins without messing with the existing bitcoin protocol.
[snip]
Trying to peg a distributed currency to an external value like gold or oil is complex, and leads to a lot of strange "what if" scenarios. I do believe it is possible, although a complete protocol description has so far eluded me.
Merged mining seems promising, however to do it without messing with the existing bitcoin might or might not end up happening, as that would involve adding a new hash value into the bitcoin blocks.
A meta-chain though could maybe do it: a chain specifically for the purpose of being the most difficult chain of a potentially large number of merged chains, the place you go to when you want to be yet another merged mining chain.
Two of the currencies my IRC bots work with are at least somewhat commodity based: GMC and GRF (General Mining Corp and General Retirement Funds). They are not really directly a commodity peg though because the corporations promoting them have not really settled yet on whether to charge interest on loans of these currencies or to simply increase the amount of a commodity they will buy per unit of the currency.
For example instead of charging miners 1% per day interest when loaning them GMC and/or GRF as capital for setting up a mining operation they might simply keep increasing the quantity of mined commodities each unit of the currency will buy, so that the currency goes up in value 1% per day. Here I mean value as in how much of a commodity they will buy per unit and also how much of that commodity they will sell per unit.
Obviously the catch in such plans is who will "honour" coins minted by miners who are not part of the corporation; thus the interest in "licensed mining" and the current practice of having customers use "thin" clients such as the IRC bots instead of having "full clients" such as the corporations and their agents (such as IRC bots) use.
It will not be until the problems around these two currencies are adequately solved that these corporations will look seriously at per-commodity currencies; the GMC and GRF currencies are more like abstractions of baskets, or a kind of "share of the commodities the corporation has available for sale".
Part of their interest in interest is the thought that possibly some of the market demend for a currency might possibly be able to derive from interest denominated in that currency being offered on bonds/loans denominated in that currency. (As they are able to charge quite high interest on loans, they could offer somewhat less interest on bonds aka loans-made-to-them.)
-MarkM-