Deleted off-topic post about features of bitshares unrelated to derivatives tracking the value of the USD (sorry bytemaster).
I largely agree with thezerg here, but I think he is missing perhaps the most important issue.
There needs to be a mechanism through which events in the real world impact events in the blockchain derivative world. Bitshares doesn't suggest any mechanism whatsoever. So it is kind of a joke.
MasterCoin does better, proposing published datastreams. That's a great idea. But why should we trust these datastreams? Clearly manipulating a datastream could be profitable if it allows me to cash out an escrow fund. So someone has to get rewarded for publishing good data. And the rewards have to be large enough that they outweigh the benefits of cheating. How does that work?
No, I've been going on and on about the trusted oracle problem from day 1. Here's first post:
Questions:
1. How does information about the price of USD in THC enter the system?
Actually, I wrote yet another big summary including all the issues (including the oracle issue) for this thread and then just lost heart, deleted it and posted the one liner.
Why did I give up? Because none of the authors are looking at the system from a theoretical perspective. What I mean is that they pick a specific algorithm and we refute it, and then they modify it.
But, given an anonymous, trustless system, ALL possible interactions can be defined. There can be no "out-of-band" interactions -- like arresting someone for example -- because the players are anonymous. All interactions are:
1. Buy from the "mint"
2. Sell to the "mint"
3. Holding
4. trade
This means that you can define classes of algorithms, and show that these classes cover all possible algorithms:
1. All algorithms that create > 100% backing (manipulation of 1 and 2)
2. All algorithms that use a fee to encourage/discourage minting/redemption based on the divergence between X and crypto-X
3. All algorithms that pay dividends, from funds gathered by 1 or 2
4. All algorithms that pay dividends by taxing, demurrage, or printing (mining) X
5. Any hybrid of the first 4.
"Normal" bitcoin volatility breaks all classes of algorithms unless such high safety margins are used that the margin becomes much larger than the pain of using the crypto currency directly. And that assumes a perfect oracle. An imperfect oracle can only act to destabilize the system...