[ By Howard Haykin ] With Bank of America reporting the closure of 154 branches and elimination of 631 ATMs in its commercial banking unit, the securities industry must be wondering:  What's in store now for the investment banking division, including Merrill Lynch? After accounting for new branch openings, the bank had a net reduction of 51 branches in the first quarter.  California's largest bank operates about 5,700 branches and 17,250 ATMs nationwide.   The moves were made as BofA seeks to improve efficiency, given that more customers embrace online and mobile banking.  BofA CEO Brian Moynihan has said the bank plans to close 750 branches over the next few years. BofA said its online banking customers in the first quarter grew 374,000 from a year ago, to more than 30 million at the end of March.  Mobile customers jumped by 2.7 million in the first quarter to 9.7 million. Any branch closures in the Bay Area, or the state's other large markets, likely will be seen as an effort to optimize the network rather than a market retreat. "Bank of America Corp. has begun exiting non-core markets through branch sales, and many more could be on the way," according to research firm SNL Financial.   [SF Business Times, 5/17/12]