Here-to-fore, I had generally accepted the meme that where Wal-mart moves in to small towns, smaller stores tend to fail due to the competition. Unlike most who spread this meme, however, my response has generally been, "so?" The number of people shoveling coal into steam boilers has decreased with the rise of diesel locomotives. The number of people employed physically connecting phone calls with patch cords has fallen with the rise of automatic switching. Technology and distribution systems change and morph over time.
But I have to admit I appear to have been wrong -- the meme itself may not be true. Via Mark Perry, who discusses this study in more depth.