Another main reason for Hollywood not to jump into a movie download business like the music industry has, is that they don't want to undermine DVD sales of movies. Also when you assess damage done by piracy, the movie industry has been nowhere near as damaged as the music industry; so you could say the music industry jumped into the legal music downloading business because it had no other choice.
Rental systems currently exist for movie downloads but they only allow users to watch the content, they don't allow it to be stored. BiBC's Boxoffice365 would allow users to download copy protected files (of course) and keep them, watching whenever they want as many times as they want. Customers can also transfer the video to one portable video device. In the near future, there will be many more services like this. Even Sony has told details of its planned "iTunes for films" service which will originally launch offering 500 Sony movies.
Source:
BBC News