I just had an interesting idea for Mastercoin Gateways.

You might be familiar with the concept of Ripple Gateways.
The primary function of a Ripple Gateway is accepting Fiat from customers, and "converting" it to "Fiat IOUs" which are then sent to clients.
You can come into this Gateway, wire it USD, and get USD IOUs in return.

Well, we can easily translate that idea into trust-less Mastercoin Gateways.

A Mastercoin Gateway would be a business or entity that accepts fiat and sends back the same fiat in the form of a CFD or backed currency.
I call it "trust-less" because once the deal is finished, you no longer need to have any trust or relation with the Gateweay, unlike Ripple Gateways which require the Gateway to keep functioning because it owes you money.

Real world Mastercoin exchanges could double as Gateways - regulation for these might vary, or might be the same, per state and regulatory environment.