Flat rate also trumps free. That's why Netflix is better than Comcast on-demand (at $1 to $5 per movie) -- I want the ability to turn off a movie after 20 minutes if it is junk, without feeling like I just wasted a couple Washingtons or a Lincoln.
Since the headlines the other day about Netflix overtaking Comcast, I predict that price is going to change very soon (but not so soon that it's seen as a proximate cause).
