Morale quickly turns ugly after a company warns about layoffs—even if the job cuts won't happen for a while.

Just announcing the intent to "reduce head count"—as Bank of America Corp. and some other financial firms have done recently—can distract workers, hurt recruiting efforts and prompt top performers to head for the exit.

Bank of America Chief Executive Brian Moynihan told employees in an internal email last week that "overall employment levels" at the bank would come down by 30,000 over the next few years.

Rumors of massive layoffs had been rippling through the ranks for months, according to one ......