I doubt Amazon, Apple, NetFlix etc are going to give you their data.. they might if you paid them for it?
Also the content providers themselves may have contracts with Amazon, Apple etc which prevents them from sharing that data with any 3rd parties and is exclusively available to them.
I don't know how analogue / digital TV ratings work in the US, but in the UK it is compiled by a company (BARB) by having a representative sample of people having their TV viewing measured by extra equipment installed in their homes and then extrapolated to give the 'real' viewing figure.
I am thinking maybe a similar idea could work for net based viewing with a desktop / browser plugin.
- Collect their demographic
- Provide an incentive for people to sign up (weekly prize draw, monthly prize draw)
- Perhaps even sell it as a social aspect (allow us to collect data on what you watch will help give you good programming in the future).
On the other hand, look at the current shift for net-based viewing - a lot of it is moving onto TV based set top boxes (Google TV, new Apple TV and integrated into TVs themselves). These are all walled gardens and I can't see you having any chance of getting that data. Apple do not even publically give you a regional breakdown on their device sales (for Europe at least), so the chances of them sharing this data are nil.