Apparently, YouTube is in talks with the major studios to "launch a global pay-per-view video service," which would let visitors pay to stream single movies. Wow, what a concept! Only pay for the privilege to watch once and save a considerable amount of money because you aren't keeping a copy of the media file.
Well, I wonder how long it will take for someone to do same thing for digital books? I think many of us entrepreneurs are thinking about it, but it's the publishers who are afraid to let go of the control and distribution of their content, so IMHO, we will have to wait several years before it becomes widespread practice and more than a niche play.
Personally, I think single stream [or single read] payments are much more economical and valuable to today's average consumer and as a result, the hipper publishers/distributors who acquire the digital rights to rent chunks and entire eBooks - are way ahead of the game in the long run.