Can you layout a simple step by step scenario with 2 users (if users are issuers not gateways) who are trading BTC/USD in Ripple?
Just a scenario if I want to sell 1 BTC for 1000 USD and then a few days later sell those 1000 USD to x BTC. I dont understand how that could work without gateways (at the end I want real BTC and real USD not IUOs - if a gateway is needed then lets add it to the scenario with all trust implications).
You are correct, it does not work without gateways. Just like there is no bitcoin trading without a bitcoin exchange. Okay, you can use localbitcoins, but even in that case, the price is agreed base on the price at an exchange. And exchanging through an individual on localbitcoins would be like exchanging through ripple where the "gateway" is an individual rather an a centralized exchange - you still have to trust them to pass you the "real money" as you pass them the coins.