I was thinking about this idea as a way for someone like Joss Whedon to try to get a complete project made. If you funded it with a few pilot episodes where the studio takes a smaller risk and the subscriber audience is proven then you might be able to get the fans to make some kind of up-front subscription commitment which could convince the studio to take a bigger risk.
I think eventually you are going to see a PPV aspect to regular TV, but it might be awhile. I personally have no regular TV service: I don't have Sky or cable; nor do I pay TV License fees as a result. I would, however, be willing to essentially buy a box set of a series in advance if it was of interest...say Star Trek?
Given how well Apple's iTunes film rental service seems to work I definitely think this idea could have legs; just need to get the kit in everyone's lounges hooked up to the 'net to make it possible (I have a Mac Mini hooked up to my TV).