The one that gets me is paying to move a file across the internet. I've still not seen a good explanation of how that is possible even given the existence of patents on the process of creating or displaying the file at either end. (And note, you still have to pay this if you charge for access to the video or your site as a whole).
They make it a condition of licensing you the ability to encode or decode the video — contract law.
If you read the EULAs and such on even a piece of 'professional' software like Final Cut Studio or Avid, it'll describe how the encoder is only licensed for personal use and that someone else in your distribution chain needs a different contractual arrangement with them, along with whoever's on the playback end.
