If you get scammed while using ripple by a user that decides to be untrustworthy there is no recourse.
Ripple is an irreversible payment system just like Bitcoin. There is no recourse if you regret sending funds or do so in error.
In the traditional banking system recourse actually exists. So I'm trying to figure out where you fix the scam portion of things when you still need to trust someone. I do not see any government or institution willing to (and able) to provide recourse to financial victims if they are scammed using ripple.
The issues for Ripple are much the same as Bitcoin. In much of the world, irreversible payment systems are already available and widely used.
Ripple may wind up being predominantly used between payment systems rather than between users directly. Ripple can provide the cross-currency and cross-issuer movement of funds without users having to interact with Ripple directly. This allows payment systems to make payments reversible between each other under whatever terms they find mutually agreeable. This also avoids the need for users to manage cryptographic credentials.