Well, it's just another one of the frauds that they perpetrate on unwitting customers. So long as the amount that they take from each victim is relatively small, they gamble that they can slide under the radar and avoid prosecution.
I'm no longer shopping there, and you can be sure that this year my 16 nieces and nephews will NOT receive the Walmart gift cards I usually give them. I think gift cards from a bookstore will probably be better for them anyway.
Several friends have told me that Walmart will never notice my boycott, which I'm sure is true...but it makes me feel better.