Wal-Mart is currently under fire (and has been for a long time) because it is alleged that the company discriminates against women in its employment practices. It is alleged that the company has policies that allow (but do not require) store managers to be able to discriminate against women. These policies, the critics say, have led to a situation in which women at Wal-Mart are paid less than men for similar jobs and women get promoted less quickly than men do.
It is important to note, however, that the current Supreme Court case regarding this is not about whether Wal-Mart is or is not guilty of discrimination. The current case is only going to decide whether all women who work at Wal-Mart and claim discrimination can be lumped together in one class-action suit. Wal-Mart argues that the women are not similar enough to be a class and should therefore sue individually.
That's interesting because even though the skills of each woman may well be different, I don't believe this is why Wal-mart treats women differently. I believe they treat them differently because they are women and I believe they see us as less efficient, not equal to and maybe not as knowledgeable as men and therefore not warranting the same pay as men.