At this point, net neutrality would be telling companies how to run their business. It's not about overusage. It's about shaping usage.
Examples are that the ISP wants to build a plan that says VoIP, NetFlix, AppleTV, Hulu, Google Play &c would be data that triggers enhanced charges to either the end user or the supplier. eg: "Dear Google: we have blocked Google Play from John Smith IP 128.99.99.99 until you cover his data transfer charges. Signed ISP."
Telling ISPs they are forbidden to do this type of discretionary pricing is the thrust of Net Neutrality, and it is absolutely legislating a reduction of their business options.
Forget throttling. I'm thinking about 'tapping into' everybody's revenue streams. For example, the ISP could request a $1 commission on Amazon.com orders as compensation for carrying their traffic. 25c per iTunes purchase.