Placing your balances in the hands of third parties means effectively government has complete control and can destroy the apple-cart with regulation and seizures at-will.
Hold on here Anon - WTF has Govt. had to do with Mt Gox going tits up ?
Read the OP. Confiscated their coins. Confiscated their bank account. Provided a court system for them to be sued for $75 million. Put regulations that forced them to shut down large portions of their former business.
But I agree about trusting 3rd parties [in the absence of regulation] being problematic.
Regulation can only make it worse. And I am not going to argue with you or explain to you further, because you are a socialist. You will never understand (agree with) the logic.
What would a decentralised exchange work like in practice ? How would it be implemented ? Where does Ethereum fit into all this ?
Cpu-only mining of any altcoin, the decentralized exchange for Bitcoin. Buy a personal computer to exchange fiat for coins. Spend your coins for goods, do not go back to dying fiat.
Or sell some good or service for coins.
Or do a decentralized exchange of Bitcoin for an altcoin, i.e. use Bitcoin's centralized exchanges.
However the problem with centralized exchanges is mostly due to people storing balances in them. If you just pass through quickly, they for the most part only present a problem to anonymity due to their compliance with AML and KYC regulations.
Regulation makes the market predictable and acts to stabilize value.
Incorrect. Regulation makes everything less predictable because fitness is stomped on, e.g.
Mt.Gox fiasco caused by regulation. Rather it is the liquidity (market cap and velocity) that make a currency predictable and stable. It may be that those have always been seen together in the past, thus people conflate them. But it doesn't mean an decentralized regulation of order (i.e. Proof-of-Work) couldn't become deep and liquid and fitness isn't stomped on because the degrees-of-freedom are unlimited still, thus being stable and reliable.