In the current "real-world" setup, money is either held by a bank and FDIC insured to $250K or advanced by a credit card company. So, there is no "default risk" unless the FDIC goes down. In the Ripple system, neither the store of value nor the transit value is insured. This seems like a real negative currently.
A .25% default risk (5% risk of the event, 5% of funds at risk) versus a 2% credit card fee, a 6% remittance fee, or a 5% conversion fee looks like a pretty good deal. But I definitely agree -- having insured gateways is even better.