WASHINGTON -- Alan Greenspan's reputation is under siege, and he's incredulous.

Hailed three years ago as "the greatest central banker who ever lived," the retired chairman of the Federal Reserve now is being criticized for his management of the U.S. economy before he retired in 2006. The Fed's low rates and laissez-faire regulatory oversight during his final years are widely blamed for sowing the seeds of today's financial crisis -- one that began in the U.S. housing market and is now battering banks, stock markets, borrowers...