Good question, anxious to see how it works in ripple. I dont understand why you would have to drive 20 TTBit DYMs out of the market. But suppose you don't offer free shipping and random_cat DYM trade at a discount to TTBit DYM. Those who hold both issues would have one DYM total balance. This is similar to BTC-E USD trading to a premium over MtGox USD because BTC-E coins are cheaper, but yet only one USD balance would display in the account.
Now, someone with TTBit DYM wants to buy something, but that person only trusts random_cat DYM. When he sends DYM, will orders be filled in the TTBit / random_cat DYM market to make it work, or will the sender be credited with XRP?
The driving TTBit DYMs into my wallet is my (speculative) ceteris paribus expectation from the asymmetry of the trust relation. With a small network, I would not think it stable since very small shifts in trust (expressed in the brain, not the software) or value could cause market makers to create very wide spreads.
My understanding from what I have read so far is that the two DYMs are completely separate currencies that happen to have similar names. That means there must be some exchanger(s) in the path(s) who charge(s) some spread.
Is the exchange function to be automatic? From reading the gateway implementation description it would appear so. I believe it was in
https://bitcointalksearch.org/topic/introducing-ripple-currency-dym-149533 that I read about the need to reserve a bit of extra for a spend to cover fluctuations.
How does one gracefully shutdown a gateway with no time limit on the debt?