The PVRBlog notes an upcoming shift in the movie rental/purchase business:

Edward Jay Epstein covers Rupert Murdoch's drive to kill off the movie rental business by adding DVRs to the DirecTV network to create video-on-demand.  The main challenge is that Wal-Mart has forced the movie companies to give physical retailers (Wal-Mart) a 45-day window of time where movies cannot be distributed electronically. Is this a Wal-Mart vs. DirecTV battle?  I can't imagine it being that simple. However, a future where we don't travel to Blockbuster (or Tsutaya here in Japan) is obvious for those who enjoy NetFlix.  With the 100 and 1000 Gb/sec. retail consumer fiber-optic networks in Asia, VoD for movies is not far away.

This is going to be a fairly big change. Right now, the rental model still works. If we have big enough pipes, and large enough storage arrays though - all bets are off. This is ultimately what the MPAA and the RIAA fear most - a basic change to the current industry model. It's not that there's no money to be made there - it's more that there's comfort in inertia.