From what I understand, it helps to prevent video ripping. I prefer HTTP streaming though; it's much easier to implement. I use the JW flash player, which supports MOV (H.264/MPEG-4) files on Flash Player 9 and above. Visitors are then able to play your videos in glorious full screen, and IE users don't need to be annoyed by ActiveX.
For more info on the JW Flash player at Dreamhost, visit http://wiki.dreamhost.com/Flash_Media_Player
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