4. General Growth Properties The commercial leasing industry might be negatively affected in the event of a default because rental space might find fewer tenants in the event of a slowdown, making it harder for them to offset high fixed costs. The list identifies General Growth Properties ( GGP) as a company that could be affected. The company, which counts Pershing Square's William Ackman as a major investor, operates shopping centers in the U.S. General Growth emerged from bankruptcy last November. Since then it has been taking advantage of lower interest rates to refinance its mortgages. That effect won't last if there is a default. Rental incomes will also come under pressure as retailers encounter poor consumer spending. Already, cautious shopping habits of consumers has hurt business. Regional mall vacancies reached 9.3%, its highest level in 11 years in the second quarter as department stores closed and retailers scaled back expansion plans according to preliminary data from Reis. Higher vacancy rates squeeze rental income, while fixed costs for mall operators remain high. Simon Property Group ( SPG) and Vornado Realty Trust ( VNO) will also be negatively affected, according to IBIS. "I'm known for checking our accounts receivable every month when I get the report. And they (the U.S. government) are always 30 days delinquent," David Simon, CEO, Simon Property Group told Reuters, commenting on the debt crisis. "But beyond that, we don't see any real risk. Spreads will invariably widen for all of corporate America and for all asset classes. So we'll be a participant in that, but beyond that, we can't see anything that's going to be anything material." Read on now for the winners.