The cases come in a variety of styles ranging from a simple tri-fold protective case, a smartcover, and even a case with an detachable Bluetooth keyboard:
So are these listings real? Probably.
Ten inch (and larger) tablets are quite a different market from 8" tablets. Because of their size, 10+ inch tablets are less mobile and are more likely to be left on a desk than say an 8" or 7" tablet (some of which can be shoved in a pocket).
As I see it, Microsoft is going after an entirely different market, one where Windows 8 tablets are having some success. Clearly Microsoft is hoping that the Surface Mini will prove more successful than the Surface, which due to its high price (the Surface RT costs more than most Windows 8 tablets from HP, Dell, etc) has largely failed to catch on.
It's also worth noting that TechCrunch broke the news with a report about 2 cases, while I am now seeing 8 listings for at least 4 different styles. This is far too elaborate to be a hoax, and the overall design of the Surface Mini looks to be the right scale for an 8" tablet.