Yes, there was the case of Netflix and Comcast for example.

The events were basically these:

1. Comcast noticed that Netflix is responsible for a lot of traffic of their private internet customers.
2. Comcast asked Netflix to pay for a better quality of service to their customers. They refused.
3. Comcast started throttling Netflix. The bandwidth available between individual Comcast customers and Netflix got worse every month.
4. Finally, Netflix caved in and paid the toll.

This example showed the validity of a new business model for ISPs: Have websites pay ISPs for better access by their customers. This would make it extremely difficult for newcomers on the market to compete against competitors who can afford to pay the ISPs. Further, ISPs could decide to flat out reject such a deal with specific websites for any reason they want. This could be ethical concerns or business interests.

Speaking of business interests, there is another business practice which is questionable from a net neutrality point of view: The zero rating. There is currently a good example for this in Germany. Monthly data caps on mobile internet usage are usually quite low in Germany. That makes it really expensive to use music or video streaming on the go. The solution by German ISP T-Mobile? Pay just a little bit extra and streaming no longer affects your monthly data cap usage. But initially only if you used their streaming services.

Under pressure from the Bundesnetzagentur (the regulatory body for data services in Germany) they caved in and offered the same zero rating for their main competitors on the media streaming market. But these are again unique deals which apply to specific competitors. Further, other ISPs in Germany (like Vodafone) have started to offer similar products. That means if anyone wants to offer a new streaming service, they would have to negotiate with all the ISPs (worldwide!) to also get a zero rating deal. This is a problem for small and specialized streaming startups who usually do not have the resources to do that.

Yes, there was the case of Netflix and Comcast for example.

The events were basically these:

1. Comcast noticed that Netflix is responsible for a lot of traffic of their private internet customers.
2. Comcast asked Netflix to pay for a better quality of service to their customers. They refused.
3. Comcast started throttling Netflix. The bandwidth available between individual Comcast customers and Netflix got worse every month.
4. Finally, Netflix caved in and paid the toll.

This example showed the validity of a new business model for ISPs: Have online content providers pay ISPs for better access by their customers. This would make it extremely difficult for newcomers on the market to compete against competitors who can afford to pay the ISPs. Further, ISPs could decide to flat out reject such a deal with specific content providers for any reason they want. This could be ethical concerns or business interests.

Speaking of business interests, there is another business practice which is questionable from a net neutrality point of view: The zero rating. There is currently a good example for this in Germany. Monthly data caps on mobile internet usage are usually quite low in Germany. That makes it really expensive to use music or video streaming on the go. The solution by German ISP T-Mobile? Pay just a little bit extra and streaming no longer affects your monthly data cap usage. But initially only if you used their streaming services.

Under pressure from the Bundesnetzagentur (the regulatory body for data services in Germany) they caved in and offered the same zero rating for their main competitors on the media streaming market. But these are again unique deals which apply to specific competitors. Further, other ISPs in Germany (like Vodafone) have started to offer similar products. That means if anyone wants to offer a new streaming service, they would have to negotiate with all the ISPs (worldwide!) to also get a zero rating deal. This is a problem for small and specialized streaming startups who usually do not have the resources to do that.