If you have been the victim of online fraud, you know that this may be outside of the realm of SL's responsibility. Of course if it involves PayPal you can file a dispute.
But - internet crime is a federal offense. You can easily report internet fraud to www.IC3.gov which is responsible for initiating a complaint to the appropriate authorities. There is no guarantee it will be investigated, but the more complaints it gets about a particular person or site, the more probable there will be action.
I was recently the victim of fraud within SL. Because of the TOS i can not discuss the details, but you can read about it on another associated website.