By Jessica Silver-Greenberg, Theo Francis and Ben Levisohn

That didn't take long. The economy hasn't yet recovered from the implosion of risky investments that led to the worst recession in decades—and already some of the world's biggest banks are peddling a new generation of dicey products to corporations, consumers, and investors.

In recent months such big banks as Bank of America (BAC), Citigroup (C), and JPMorgan Chase (JPM) have rolled out newfangled corporate credit lines tied to complicated and volatile derivatives. Others, including Wells Fargo (WFC) and Fifth Third (FITB), are offering payday-loan programs aimed at cash-strapped consumers. Still others are marketing new, potentially risky "structured notes" to small...