Former Merrill Lynch chief executive officer John Thain, who recently was head of the brokerage's wealth management and corporate investment banking divisions, resigned today.

The announcement came after a morning meeting between Thain and Bank of America chief executive officer Kenneth Lewis, during which the two men discussed Thain's future at the company, according to CNBC. It also coincided with the combined company's plans to lay off employees from its investment banking business.

Merrill Lynch and Bank of America did not return calls seeking comment, but a public statement from Bank of America said Brian Moynihan was named as president of global banking and global wealth management and investment management.

Moynihan, general counsel for Bank of America, is no stranger to wealth management, having once served as president of global wealth and investment management at the bank.

Despite the recent departure of Thain and Robert McCann, the former chief of its brokerage unit who resigned Jan. 6, Lewis sounded a positive note about the future of the Merrill Lynch brokerage unit. "Those organizations, which formed the heart of Merrill Lynch, will continue to serve their clients as world class financial service providers," he said in the company's public statement.

But an outside wealth management analyst painted a different picture, saying that Thain's departure will be devastating for the brokers that remain at Merrill Lynch because they will not have an influential senior executive to negotiate for them at Bank of America. "Ultimately the top caliber navigating that big ship is gone," said Alois Pirker, a wealth management analyst for Aite Group. "If you cannot retain the integrity of that brokerage unit or of the investment banking unit, you lose the value in it."

This move also underscores the ongoing march of Merrill Lynch's top brass and its rank-and-file brokers toward the exits. In addition to Thain and McCann, since Merrill Lynch's acquisition by Bank of America was announced late last year, the company has shed about 760 financial advisors from its wealth management business, according to Merrill's fourth-quarter filing with the Securities and Exchange Commission.

Thain's decision comes scarcely one month after Bank of America completed its $50 billion acquisition of Merrill Lynch, partially subsidized by a $20 billion handout from the federal government. After the fuller extent of Merrill's troubled assets began to come to light, Bank of America was forced to accept protection from further losses on $118 billion in risky assets, mainly from the former Merrill Lynch portfolio, according to Bank of America's fourth quarter results.

Merrill's weakened financial condition put a strain on the relationship between Thain and Lewis, according to press reports, as did reports that Merrill had paid out cash bonuses days before its acquisition by Bank of America, and Thain had spent $1.2 million redesigning his office.

Divergent corporate cultures and conflicting visions on how the newly merged company should be run probably played a part in Thain's decision to leave, said Andy Tasnady, managing partner of Tasnady & Associates, a Port Washington, N.Y.-based compensation consulting firm. Financial entities like Bank of America operate with a much more centralized decision-making structure than brokerage and securities firms, and they offer smaller compensation packages, explained Tasnady. Another possibility is that Thain may have been a "scapegoat for the degradation in Merrill's fourth-quarter results," said Tasnady.

Thain caused a public uproar stemming from the compensation issue. In early December, weeks before the takeover by Bank of America would be finalized, he approached the Merrill Lynch board of directors and argued that he deserved a bonus of as much as $10 million. After harsh criticism from all corners, including the New York Attorney General Andrew Cuomo, who called the request "nothing less than shocking," Thain withdrew that request.