Replying to Digital copies of movies sold with the movie??

So, like an excited little school girl, that I am, I went out and bought Harry Potter V. And not just any copy, but the special edition DVD... which really didn't have too many great features. However, one of the "special features" is a digital copy of the movie to download onto your computer for your ipod, psp etc. The 'security feature' is a one-time use code to download it. What's the deal with this?! Would this not result in decreased sales later on?! I'm pretty excited I have two copies on the movie now though. I'm not complaining! Is this a new thing or have I just been missing in action for this bandwagon?! I've never heard, nor ever thought, that WB would distribute this, mind you, I ended up paying $32 (taxes in) versus $25.