Insurance Fraud

Inspired by the used engagement ring thread: what protects insurance companies from rampant fraudulent claims with regards to stolen diamonds? I bought my wife a 2ct. engagement ring and it is insured for about $3k more than I paid. Morality aside, what is keeping us from having the ring "stolen" and getting a windfall?

I share Los Feliz Slim's feeling that it probably isn't as easy as it sounds...