This system from T-Mobile has a different incentive structure behind it though based on what I heard. Netflix and Hulu are NOT paying T-Mobile, they are just cooperating to make sure their data is not counted against T-Mobile's customer's data usage caps, which increases the value of all three companies services. T-Mobile has an incentive to offer this deal to any web-service that is well known and desirable enough to their end-users that offering access without a data cap improves the apparent value of T-Mobiles service.
And therein lies the rub. T-Mobile decides which services qualify exemption from data caps, which violates the principles of net neutrality. For example, if I have a server set up somewhere to stream video for my own personal use, would that be exempt from data caps? Unlikely, because who the hell am I? Yes, I can also see a future where an up-and-coming service might not qualify. All traffic should be treated equally by the ISP. If T-Mobile thinks it can handle the additional traffic, they should raise data caps. BTW, I am a T-Mobile customer.