Wherever there are finite bandwidth connections, there will always be throttling. Whether the throttling occurs based on type of traffic, end user limits, or "naturally" sort itself out via TCP or other protocols, throttling will occur as the bottlenecks fill up. If the carriers will not be allowed to do any throttling based on traffic type/source/etc, then the guy that decides to run a p2p file server will have his 500 connections open while your measly 1 netflix connection will get drowned out, as the "natural TCP throttling" tends to divide the bandwidth equally per connection (not per user). Then people will complain about the quality of service, but it will be neutral. What people are really wanting here is "don't throttle me", but that obviously cannot be satisfied for all users.
On the other hand, the providers can implement another type of throttling - financial. Once they start charging you for bandwidth used, folks considering watching a netflix movie for $x per show may start throttling themselves.