Americans are friending credit unions as they grow increasingly frustrated with fees and customer service issues stemming from the nation's larger banking institutions.

At least, that's the conclusion of a new survey conducted by the National Association of Federal Credit Unions.

As for what led to the ascendancy of credit unions and smaller banks, NAFCU credits Bank Transfer Day and Facebook. Last November, users of Facebook promoted the national Bank Transfer Day, encouraging consumers to move from banks that push excessive fees to credit unions and smaller firms. 

Fifty-six percent of the credit unions surveyed reported strong membership growth in the past 12 months, NAFCU said. And more than half of the credit unions attributed their recent growth to Bank Transfer Day.

As for why consumers transferred their funds to credit unions, the majority, or 46.7%, cited dissatisfaction with the banks. Others said they left for better loan and deposit rates as well as lower fees.

"It has been nearly a year since Americans frustration with banks' excessive fees and poor customer service led to a mass migration to credit unions in the Facebook-fueled Bank Transfer Day," said NAFCU president and CEO Fred R. Becker, Jr. "Our data confirms that consumers who gravitated to Main Street credit unions stayed because they found true value through unparalleled service, lower fees and competitive rates."