Sure. All things are assigned a class in VW whether you want them to be or not. Even the none class is, essentially, a class. If you create a viewport, it's class will set itself to the active class. This can ( and has ) create a problem if you don't pay attention to which class you have active. You might end up creating a viewport and then not be able to find it if you've turned the class off while doing something else.
I can't think of any time when I'd want a viewport to be in a class other than a "viewport" class, although I've such things before and immediately contradicted myself. But for now, I'd like to be able to set a preference that defaults all viewports upon creation to the class of my choosing.