Bank Transfer Day seems to be getting some traction.

The Credit Union National Association reports that more than 650,000 customers have transferred some $4.5 billion from big banks to credit unions in the last four weeks. Credit unions are not-for-profit financial cooperatives that often charge lower fees than giant banks - and they appear to be benefiting from the backlash against debit-card fees and other nuisance charges that some of the biggest commercial banks tried imposing earlier this fall.

Of...