A single definition can be worth billions under the law, and nowhere is this more obvious than in the rights industry.
This became apparent with the final ruling on the 'Cablevision DVR' case which handed a massive win to cable operators and content distributors.
You see, the problem with running a cable TV or IPTV service is that you have to build, install and maintain complicated and expensive boxes that are these days a bit like PCs; these boxes need to run 24 x 7 x 365 and you need to update them regularly.
All of the intelligence of the cable industry is currently transferred to the living room before the viewer can benefit from it.
Broadly speaking the Cablevision DVR ruling states that there is no difference between a viewer recording something locally or recording something remotely.
So, as we move into a world where all 'TV sets' will have a broadband connection and a processor, the cablecos are now free to get rid of these pesky boxes. If you want to 'record' something in reality all the cableco/IPTV service has to do is to tag this on a server. When you play your 'recording' all the tag does is call the video file. Much cheaper and much easier - and frees a lot of the cable capacity.
But back to definitions - what's the difference between a 'tagged PVR recording' and a 'video on demand'. As far as I can tell, and as far as the US Courts seem concerned, there is none.