> This if course doesn't not mean there are zero deab people still receiving checks. With any system this size some fraud will exist, the question is how much, and how much does it cost to chase down.

Right, it's an optimization problem. You fight the fraud to the point that it optimizes loss. If it costs $1 million to stop $10 million of fraud, you do it. If it costs $1 billion to stop $10 million of fraud, you let that fraud happen.