[talmand]

No. If you don't return the physical media then chances are they'll charge you the full price, not allow you to rent again, and/or track you down because you most likely gave them your contact info.

[ben0x539]

But they don't have a mechanism in place that makes sure I remove the copy of the movie from my computer after I return the physical medium.

[talmand]

While true, copying a DVD to your computer is not a trivial enough exercise for most people to accomplish, for the U.S. at least.