The latest Bloomberg Businessweek offers a valuable lesson about moral hazard.

If there’s one thing Americans should have learned from the recession, it’s the importance of diversifying risk. Middle-class households had too much of their net worth tied up in their homes and were too exposed to stocks through 401(k)s and other investments.

Despite the hit many Americans took, there’s little sign they’ve changed their dependence on homes as the mainstay of their wealth. Last year, Christian Weller, a professor at the University of Massachusetts, looked at Federal Reserve data for households run by those over 50. The number of families with what Weller calls “very high risk exposure”—a low wealth-to-income ratio, more than three-quarters of their assets in housing or stocks, and debt greater than a quarter of their assets—had almost doubled between 1989 and 2010, to 18 percent. That number didn’t decline during the deleveraging years from 2007 to 2010; its growth just slowed to a crawl.

The Fed will conduct a new wealth survey in 2013, but don’t look for a rational rebalancing. The same pressures that drove families to save less before the recession are still in place: low income growth, low interest rates, and high costs for health care, energy, and education. Families have been borrowing less since 2007, but the rate of the decline has slowed. As soon as banks start lending again, Weller says, people will put their money back into housing. “The trends look like they’re on autopilot,” he says. “They don’t suggest that people properly manage their risk.”

The lesson? Fail to address the cause of the moral hazard, and the hazard persists.