In a recent decision, the US Supreme Court ruled that the Fair Labor Standards Act does indeed provide protection for employees who complain or ask about wages orally.  The federal courts have disagreed on this issue for decades.  They all agreed that the FLSA protected employees who complained in writing about wages.  But, several courts found that the 1938 statute did not protect employees who complained verbally.   See Supreme Court decision.  The court voted 6-2 in favor of the employee. 

As the Court pointed out, the act was passed at a time when many workers were illiterate.  Just over 20% of manufacturing laborers in 1940 only had five years of schooling.  It was often simply not practicable to write up complaints in a workplace where work sites were dirty and special clothes were necessary.  Kasten v. St. Gobain Performance Plastic Corp., (3/22/2011). 

And, of course, truly, few employees would have the nerve to complain in writing.  But, many employees do indeed ask simple questions about wages and then suffer reprisal.  One of my clients once noted that a big box store failed to pay overtime to some seasonal employees.  My client simply asked one of the managers if that was kosher?  The client really thought he was just trying to help management and the workers.  Big box store never asked him to return – he was a seasonal employee himself.  If this decision had been issued sooner, that client could have filed some legal action about their reprisal against him.