If you download a movie from the PlayStation video store, make sure you don't delete it.
A user on the Ars Technica forums had to remove a movie to make some space and was unable to re-download it. "I tried to back up the videos, you can't," said the user 'Noise', "If your PS3 dies or hard drive dies you lose."
To be fair to Sony, the PS3 Support Page does confirm: "Content cannot be redownloaded once it has been downloaded to either a PLAYSTATION 3 or PSP system." but this will still leave movie fans in the lurch if they accidentally delete their downloads or decided to swap out their hard drive for a bigger unit.
Sony say that they will grant one additional courtesy download (if you ask nicely) but that's your lot.
PlayStation 3 video DRM: two strikes and you're out [Ars Technica]