Do we need labor unions to counterbalance the power of big corporations?

S. Labor Force was unionized in the mid-1950s. By 2011, union membership had declined to slightly more than 10%, a 70-year low.
According to the Pew Research Center, while overall 64% of Americans believe unions are necessary to protect the working person, 57% agree that “labor unions have too much power.” (Pew Research Center, Trends in American Values. Released June 4, 2012)http://www.people-press.org/2012/06/04/section-5-values-about-business-wall-street-and-labor/ Retrieved June 13, 2012.
After reading pages 604–608 in the text, as well as any other outside material you may find, consider the following.
Do we need labor unions to counterbalance the power of big corporations? Explain your answer, and provide links to any outside material you found useful in forming your answer.