This post
https://bitcointalk.org/index.php?topic=203647.msg2210023#msg2210023sparked an idea - What if an exchange let you trade with coins that you haven't deposited yet, by giving the exchange something else of equal or greater value, temporarily.
Example, you want to deposit 10 SlowConfCoins (tm) to sell for USD as soon as possible, so the exchange lets you first deposit 10 LTC as security while the slower coin gets confirmed.
You can then trade SlowConf for USD on the markets immediately, and then when your actual deposit gets fully confirmed you are refunded your LTC security (or have the option to just add it to your LTC balance).
In fact, if you already held a balance of BTC on the exchange, they could do a quick db-based transaction pulling a certain amount of BTC aside as security instantly, while the SlowConf comes in, and then unfreeze that BTC once your alt deposit is fully confirmed.
