It took awhile to shake out, but the DRM nastiness associated with the Sony Video Store is becoming an issue now that those tiny PS3 hard drives are beginning to fill-up. Turns out that if you delete purchased video to free-up space then you'll have to place a call to Sony customer service to authorize a one-time only re-download from your PSN download list. Not too horrible, after all, you can just swap out the hard drive yourself and then migrate all your video, right? Probably not -- as spelled out by the terms and conditions of Sony's Backup Utility:
If you perform any of the following operations after backing up, copyright-protected video files in the backup data may not restore correctly.
  • Format the hard disk
  • Restore the PS3™ system
  • Move copyright-protected video
  • Download copyright-protected video
  • Play copyright-protected video that has a time restriction for the first time
In other words, your PS3 (and up to 3 PSPs) owns the purchased video, you do not.

Read -- PS3 redownload limits
Read -- Sony PS3 Backup Utility