Not all banks are equal. Many of the biggest ones have a tendency towards behaviors that can (ahem) sink economies if government is unwilling to regulate. By choosing banks or credit unions that do not engage in such risky practices, we save our own money, but we can also reduce the likelihood of having to bail out banks with taxpayer money. If we do it en masse, we can also register our displeasure with our corporate overlords.
Here is a way to search for institutions with safer habits.
Here is some additional information:
And the facebook event: