ISPs would like to charge a fee from services that produce a huge amount of traffic, to carry that traffic to their consumers with a higher priority rather than mixing it in with all the other content. (Some people worry that ISPs would throttle high-bandwidth content lower than other content to force the services to pay to avoid degredation.)
Note that large ISPs have done this for years, via in-ISP CDNs: if you have enough content, it makes sense to have copies of it to serve up directly from the ISP's network.
The primary concern I've seen raised by network neutrality advocates: because many people have very few available high-speed ISP choices (one cable provider and sometimes one fiber provider, since most people can't get competitive DSL), it may not work to just say "pick another ISP if you don't like what yours does". (That assumes enough ISP customers care enough to switch ISPs over this issue.)
Note that large ISPs have done this for years, via in-ISP CDNs: if you have enough content, it makes sense to have copies of it to serve up directly from the ISP's network.
The primary concern I've seen raised by network neutrality advocates: because many people have very few available high-speed ISP choices (one cable provider and sometimes one fiber provider, since most people can't get competitive DSL), it may not work to just say "pick another ISP if you don't like what yours does". (That assumes enough ISP customers care enough to switch ISPs over this issue.)