If it seems as though sub-prime mortgage loans stirred up trouble in the financial markets, just wait until debt problems spill over onto household spending. According to economists Barry Cynamon and Steven Fazzari, America's love affair with consumption has been a big source of economic stimulus for a long time. But the party might be about to end. Americans' overextended wallets could trigger the most severe downturn in economic activity seen since at least the 1980s — and possibly since the Great Depression.