Monroville said:

Digital downloading will fail when it comes to customer service and replacements, as it will be harder to prove a download was unsuccessful or faulty (as companies would be wary of someone wanting to try to get a movie 2 or 3 times for one price).

Services like iCloud are changing this -- once you purchase a movie, you can download it again and again from the cloud for free, as long as you're still using the same iTunes account. This feels far more secure to me than risking a failing HDD or even losing a physical disk -- and I have access to it on all my screens (TV, computer, iPad, iPhone, etc.) as opposed to only the ones with a Blu-Ray player attached.