Recession was preceded by the bursting of the credit bubble
This recession was preceded by the bursting of the credit bubble (especially housing) leading to a financial crisis. And there is research showing recoveries following financial crisis are typically more sluggish than following other recessions. See Carmen Reinhart and Kenneth Rogoff: "The Aftermath of Financial Crises" [PDF].
An examination of the aftermath of severe financial crises shows deep and lasting effects on asset prices, output and employment. ... Even recessions sparked by financial crises do eventually end, albeit almost invariably accompanied by massive increases in government debt.