In 2010, 56% of newly issued securitized mortgages were on retail properties, according to Darrell Wheeler, head of CMBS strategy at Amherst Securities Group.

WSJ: Bond Investors Strip Malls Off Shopping Lists

Still, at current prices, investing in certain subprime bonds carries "limited downside and possibly substantial upside, " said Joe Walsh, president of Amherst Securities Group, a broker-dealer that focuses on mortgage debt.

WSJ: Toxic? Says Who? Taste

Since then it has fallen back to 65.5%, and Laurie Goodman, an analyst with Amherst Securities, reckons it would be 63.3% after excluding 2.8m homeowners who are in, or probably heading towards, foreclosure.

ECONOMIST: The housing market