Stories which have zero credibility, and even less now that BB is saying they will have launch stock. If supplies were limited Apple would not be sharing stock with non-Apple stores.
This assumption is based on what, exactly? The stories are no more or less credible than the Best Buy ones--which have not disclosed which locations or how many they'd stock. In large parts of the country, there are no Apple stores, and having a launch partner to triple the number of physical locations selling on the 3rd doesn't mean there's an inexhaustible supply, just like it didn't mean so with the iPhone, where AT&T stores were given only a small number to spread around.
Walk-in supplies are going to be limited, any way you slice it. With about 200,000 reservations (an average of 700 per store), the 200,000 preorders, and just 50 units per Best Buy location and Apple Store, that's just shy of 450,000 units total--already far more than manufactured at the iPhone launch. Even if 250,000 of the 270,000 iPhones sold on day one were sold in person at Apple stores, that's 880 per store (pretending that all 284 stores were open in 2007), which is obviously more stock than Apple stores had, and Apple stores were
stuffed with iPhone boxes, which are 3-4 times smaller than iPad boxes. If iPad reservation numbers are anywhere near accurate, there just isn't
room to stock a lot of extras.
Remember that with the iPhone launch, there were no reservations. It may be that nearly everyone who actually wants one has made a reservation already, so the competition for walk-ins won't be that tough. It would also make a lot of sense to assume that anyone who wants one on the 3rd placed a reservation or preorder, and therefore there's no need to carry lots of extra stock. There's no way of knowing ahead of time.