Good question. The main problem with all of these is proof. How do you determine intent of a dropped packet? Was it congestion, a hardware failure, or did the ISP have it in for that packet specifically? The guy screaming "I'm gonna kill you!" is the top suspect when someone turns up dead, but the cops still have to prove he did it.
When Comcast was using Sandvine Comcast denied, denied, denied that they were doing anything to degrade their users' internet experience. It took the EFF and a massive coordinated traffic logging effort to prove that Comcast was lying about intentionally disabling Lotus Notes (and BitTorrent) connections.
There is very little technical reason for a byte of amazon to cost more than a byte of wikipedia. Once those packets reach the backbone networks (a process that Amazon and Wikipedia both pay for through their ISPs) they're essentially identical, except in the fact that Amazon has more money and they have more to lose if something were to happen to that packet, and that would be a real shame.
The original plan was simply "neutrality". All bytes are equal. More bytes can cost more money, but those additional bytes are equal too.
And that's where it started falling apart. Bytes delivered by copper all cost the same, bytes delivered by fiber all cost the same, bytes delivered by avian carrier all cost the same. Bytes delivered wirelessly... well, they cost the same too but some major neutrality players were doing deals with telcos to provide some services free on phones. Which was more important to them, neutrality? Or getting wikipedia to the mobile masses with no data charges? Well, as long as the net was mostly neutral (except when it suited them) it's a good thing, right? But hypocrisy is the moral rot, and rot spreads quickly.
Personally, I have two horses in this race: in my personal life I'm an internet user, at work I develop web applications. I had my experience with value-subtracted ISPs years ago. Before Time Warner traded an agreement not to compete here with Comcast for an agreement from Comcast not to compete elsewhere, one of our customers had Time Warner Cable at their office. One day I get an angry call from them that we're down. I check the status of our servers and say "no, we're up" and they insist we're down and I ask them if we're down why are they the only customer calling me. They insist. I do a traceroute from the development server and everything looks fine to me. They continue to insist. I remote into their computer and sure enough, the application isn't loading. I open a ticket with our colocation facility to let them know that some routing is fucked up specifically between IPs A and B. It's closed: nothing wrong. I tell them to call their ISP. TWC insists its on our end. I roll my eyes and mirror their database on the development server and call it a day. Day 2: we're "down" again. Neither the main server nor the development server are reachable from that customer now. TWC insists its on our end. I set up a mirror on our mail server. Day 3: we're down again. We have a three-way call with TWC. TWC insists it's on our end. I tell them that every single one of our customers using DSL are having no problems at all and offer to pay the cancellation fee so our customer has internet that works. (By this time I had reviewed all of our server logs and discovered that they were literally our only user in the city coming from TWC, everyone else had DSL). Tier 2 support is on the phone in 15 seconds. Now, this is probably about a decade or so ago, so these are not the exact words used but I won't forget the general gist of it any time soon:
Tier2: We changed a setting in their router to allow them to access their "business application". Everything should be fine now
Qz: Thank you. For future reference if we have other customers on TWC what setting is this so we can make sure it's configured correctly and avoid this problem in the future?
Tier2: Oh, it's not a setting that the customer can change.
So, what is the intent of a setting that blocks access to an ISP user's commonly used websites?