FOR more than a decade, the American real estate market resembled an overstuffed novel, which is to say, it was an engrossing piece of fiction. Mortgage brokers hip deep in profits handed out no-doc mortgages to people with fictional incomes. Wall Street shopped bundles of those loans to investors, no matter how unappetizing the details. And federal regulators gave sleepy nods. That world largely collapsed under the weight of its improbabilities in 2008. But a piece of that world survives on Library Street in Reston, Va., where an obscure business, the MERS Corporation, claims to hold title to roughly half...
