Yes, Apple will do that.Just an FYI, Apple will allow you to redownload all of your purchases as a one time exception (as in once in the lifetime of your iTunes Store Account)
Go to http://www.apple.com/support/itunes/ to ask for it.
However, what I am trying to describe is a new business area that Apple could enter. That is providing a backup service for iTMS customers for a small monthly/annual fee or on a per movie/song basis. The cost to Apple is network use (bandwidth to transfer the files) and small management overhead.