On one hand, the $130 billion he spent on acquisitions – FleetBoston Financial Corp., MBNA Corp., LaSalle Bank Corp., Countrywide Financial Corp., Charles Schwab Corp.'s (Nasdaq: SCHW) U.S. Trust private banking unit and Merrill Lynch – that more than tripled the size of Bank of America, making it the largest U.S. lender both by assets and deposits.

On the other, his open-wallet policy and the example it set forth almost perfectly encapsulates the boom, bust and nascent rebound of the U.S. housing and banking crisis – which later became the financial plague that devastated markets all over the world.

In the second half of 2007, the extent of the U.S. housing crisis began to crystallize when Countrywide's freewheeling subprime-lending policy irreversibly sank the nation's largest home lender. Lewis moved in and acquired the troubled lender for $4 billion the following January, and in doing so, he put Bank of America on the hook for Countrywide $1.5 trillion loan portfolio.

In the second half of 2008, the extent of the how much havoc the destruction of investment banks and brokerage firms would wreak upon the world became clear. The vortex of it was Sept. 15, the day the Lehman Brothers Holdings Inc. (OTC: LEHMQ) declared bankruptcy and Bank of America agreed to pay $29 billion for world's largest brokerage firm, Merrill Lynch, which probably would have failed had it not found a partner.

Lewis' spending got Bank of America into this mess. The question now is whether continued  spending – using the $45 billion bailout courtesy of the U.S. Treasury's Troubled Asset Relief Program (TARP) – will get BofA out of it.

And Lewis seems to acknowledge both in the news release announcing his voluntary departure.

"Bank of America is well positioned to meet the continuing challenges of the economy and markets," Lewis said. "We are in position to begin to repay the federal government's TARP investments.