In my fly-over town I have 4 Super-Walmarts within 30 minutes of me and there are still as many Grocery stores around as when we only had 2 Super-Walmarts several years ago. There have also been quite a few smaller grocery stores popping up yearly, especially tiny ethnic markets. If your premise is true, and I'm sure it is to some extent, it isn't having a very big impact in my neck of the woods.