Very, in my opinion. It goes beyond throttling, ISPs could also choose what sites they carry and what types of traffic they carry. It would create a backdoor in censorship laws and regulations. An ISP could use any excuse, such as cost, bandwidth utilization etc. to suppress anything they see fit. It goes beyond just websites, VPN traffic, TOR traffic, and similar privacy technologies would also be at risk. Think of the implications. Open-source software? Bitcoin and cryptocurrency? Torrents? What if ISPs decide not to carry the traffic or charge prohibitive amounts of money to carry the traffic? With Net Neutrality internet access is regulated as a utility, like electricity. Just like like a power company can't refuse to provide you with electricity, ISPs can't refuse to provide full internet access to you. Net Neutrality isn't just about internet access, it also protects our civil liberties and right to free and fair access to information. It also stifles innovation. If you're a startup, how could you compete with companies like Facebook or Google who can afford to negotiate contracts with ISPs and pay for full access? What if a company like Facebook uses their influence and capital to get ISPs not to carry sites critical of them or competing with them? How could Linux and other open-source projects afford to compete with companies like Microsoft and Apple? Those companies could certainly afford it. A handful of companies would control what you see and can access on the internet. Open access to the internet is vital to freedom and democracy.