Apparently, Nvidia is enforcing its Green Light program, which requires graphics card makers to send in their designs for Nvidia's approval. The approval will not be given if certain noise, power, voltage and heat levels are not met. Without that approval, those cards cannot be sold. Bright Side of News said that EVGA was one of the first to feel Nvidia's whip and had to remove the EVBot voltage control tool from the EVGA GTX 680 Classified.
Of course, it's easy to chastise Nvidia for this type of control, which will not allow extreme graphics cards configurations anymore. However, Nvidia's brand and perception are exposed with every card that is sold and it is understandable that the company wants to make sure that it is represented in the way it wants. Extreme designs that go overboard are unlikely to meet the specifications of Nvidia's marketing promises and are likely to be shot down.
It's not exactly what the enthusiast's heart desires and it most certainly impacts the creativity of vendors, which will have an even tougher time to differentiate its parts from the competition. But if you argue from Nvidia's point of view, then - if the Green Light report is true - the company surely has a case.