You know, if it was Intel instead of NVidia, you can bet there would be lawsuits, investigations, and government fines.
But, I can sort-of see NVidia's reasoning. They believe that they have superior products and they don't want Company ABC to have a brand XYZ that can have either an Nvidia or AMD chip in it. Why? Because they think that brand XYZ on the box has a strong appeal in the minds of consumers, so consumers will be drawn to brand XYZ regardless of the underlying technology. There are many companies that do take advantage of branding to sell inferior products to mindless consumer all the time. However, what they're also saying is that they think PC gamers are of the same ilk when it comes to buying graphics cards. So, if you're a gamer, regardless of whether you prefer NVidia or AMD, that should piss you off more than this being some anti-competitive marketing practice.