The owner drove drunk and totaled his car. He made his way home somehow and called in the car as stolen to the police. By doing that, he enjoyed a lower deductible, not being charged with an at-fault accident, and escaped a DWI charge. A similar scenario played out for hit and run accidents. The same scheme works for a digital signature.
Someone enters into a transaction they have second thoughts about.
So they report the digital signature as stolen. With no physical evidence to examine, swindlers may succeed. At least with alleged stolen cars, an investigator has the vehicle to work with. Even harder to do with credit cards, the handwritten signature acts as an evidentiary roadblock. But in cyberspace, this scam could cause problems for digital signatures.