I thought that they were already doing this. Maybe I just remember an article that said that they were thinking about doing it.
We're not sure how they are checking that you and your friends aren't just sharing all your discs so that you can all have a huge movie collection for just $2 a pop, but we're betting they have some way of doing that (or they just don't care).
My guess is that they figure if your friends have them, then you could just rip them anyway, and this way they get $2/movie out of it.

I wonder how much money the studios get from each one.
EDIT: Oh, and one other thing. If I would actually have to physically go into Walmart and spend time in there *shivers*, then they should be paying me to do this.