Why would it be illegal? If Best Buy didn't want to stock a physical product that made it easier to buy things online instead of getting them at Best Buy, why should they have to stock it?
One key distinction might be that Best Buy doesn't appear to be an open marketplace. Best Buy has to purchase from the maker, to sell, whereas app marketplaces do not purchase, they just make available. I don't know if that has any standing in court, but it's important that we recognize that the brick and mortar comparison does fail to completely encapsulate what we're talking about.
