If you think Wal-Mart wages are bad in the US, try working for their stores in Mexico. Child grocery baggers at their supermarkets throughout Mexico are paid exactly... nothing. That's right; they receive no pay  despite Wal-Mart de Mexico's $1.1 billion in profits last year. Wal-Mart refers to these workers as "volunteer packers" and encourages gratuity from customers. Aside from being a heinous practice, what does this have to do with labor in the U.S.?
This is just the extreme version of unpaid labor forced on Wal-Mart employees. Wal-Mart has repeatedly lost in state court as employees have sued for unpaid  wages , including pretending janitors at their stores were "independent contractors"  to avoid paying legally required wages. States occasionally crack down on these wage violations, but a lot more needs to be done.