"One of the things you sometimes see with activity like this is sometimes it is the beginning of signals of a corporate campaign," said Kevin Elliott, a senior vice president in charge of the labor practice at the public relations firm Hill & Knowlton.
Through corporate campaigns, he said, unions seek "to injure the reputation of the employer" as a means of pressuring them to allow unionization.
"The union squeezes the employer," Elliott said. "The employer says 'What do we have to do make this stop.' The union says, 'Give us more flexibility with organizing your workers.'"
Elliott said that while that's not something he sees happening with unions and banks right now, employers always have to be on guard for it. Banks may have to decide whether unions are, indeed, seeking to organize their employees or are just seeking to gain attention for their causes.
"If it's the former, you'd better get serious (and) make sure you're not going to be vulnerable," he said. "If it's the latter, then it is what it is."