Imagine a trillion-dollar market that runs on faxes and phone calls while routinely tying up investors' money for months before they get any return.

That's not fiction: It's the unregulated market for leveraged corporate loans. In a financial system that is increasingly automated, the origination and trading of loans is in the relative dark ages while money pours in from mainstream investors such as Kansas and New York pension plans and mutual funds catering to individuals seeking high yields in an era of near-zero interest rates.

The antiquated structure of a market that's ballooned from a mere $35 billion in 1997 poses a growing threat, raising the odds of gridlock in a downturn when investors expect to get their money back with a click of a button. As of yet, no regulators have taken responsibility for fixing the deficiency.