Let's go back to the financial crisis and the practices that brought this country to its knees. Banks developed a fancy scheme whereby they absolved themselves of all risk from the loans they made. They simply wrapped them up in a bundle and sold them to someone else. What they were doing is essentially packaging and reselling "junk."
When the news of how bad things were became known, the markets froze and collapsed. No one knew who had which securities, and if they did, they didn't know their true value.