You might remember that just a few weeks ago, a line of scented laptops were announced. And while that is certainly different, it's not exactly a true product draw. That's why I can't understand why someone would want to make a scented DVD, but that's precisely what's happening.
The Rub and Smell discs have a scented ink on the surface, so consumers can associate a particular scent with a particular film. The idea behind these discs is to increase "product awareness" and utilize the strong memories associated with aromas in encourage purchasing decisions.