I'm not sure what you thought I'm claiming.
> As someone who traded large volumes of commodities, currencies, and their derivatives, this is false. Most trading of these assets happens OTC, between private parties, and never touches an exchange.
I was not claiming that it does happen in an exchange. I was claiming that the banks were (successfully, for years) doing everything in their power to stop such an exchange from forming - do you think that is not true?
I was claiming that the big banks own the existing exchanges, currenex, hotspot, EBS, is that not true? (I've been out of the game in the last 3 years, the player names might have changed -- but I'd be surprised)
I have first hand experience of big banks exerting their influence on those (supposedly anonymous) exchanges to kick participants out when their trading style was not compatible with the banks' interest.
> This is far more de-centralized and efficient than having it happen on exchanges.
De-centralized, yes. Efficient? Only for the other party (which is a bank, the vast majority of the time).
If you want to change swiss francs to USD, and I want to change USD to swiss francs, if we had a two sided market ("an exchange") to meet in, we'd find each other, agree on a public, easily discoverable price, and that's it; The one of of us who was smarter (or could wait longer) would earn the spread, the other one would pay it; alternatively we would meet at the mid price, splitting the spread. This happens all the time in exchange traded shares, commodities and futures.
However, the way it works today OTC is that instead you and I both find a big enough player (e.g. JP Morgan, or Goldman, or whoever), who makes a market in the currency - buys at the lower price, sells at the higher price, earning the entire spread, always. Unlike either of us, that player -- by virtue of its size and position -- knows the "buy" and "sell" orders of a lot of the smaller players, and can react accordingly.
> s someone who negotiated the rate at which he changed his Swiss francs into US Dollars at a JP Morgan Chase branch in New York, it isn't a regulatorily locked market. Having a private banking relationship will lower the threshold for negotiated rates, too
That's exactly my point: You would expect an exchange that would make this into a symmetric, competitive, information efficient market because there are hardly any regulatory issues (compared e.g. to running a stock or commodity exchange). The fact that this hasn't happened in 500 years of modern exchanges is a testament to the stronghold that banks have on currency trading.
Note that such exchanges have appeared for everything, from bandwidth to energy to pork bellies - but only in a very limited way for currencies (controlled by the same old boys network), where it is easiest to start such an exchange, and such a market benefits everyone except same old boys.