Well it would depend how the internet suppliers would want it to be. As a person who lives in Portugal, where there is "no net neutrality" as many are claiming, I can tell you my personal experience with it:
- There are no speed issues whatsoever regarding visiting site X or site Y, the restrictions are imposed by the supplier and depends on the speed you signed with. There are also no traffic limits for home internet, just mobile data plans.
- There are restrictions on the sites you can visit (e.g. I can't visit most torrent sites, since they have been flagged by Vodafone, with whom I'm under contract).
- Mobile data is a bitch, and the main problem here concerns this issue. Cell phone networks have created additional packages and are charging more for extra access to a particular app. For instance, if you use social media a lot, you can pay X to get extra mobile data but just for FB, IG, Twitter, Snapchat, etc.. This is just an add-on, not the whole data plan. Their logic is if you exceed your data plan you still have mobile data for your social media needs. If, however you're stranded in the middle of the woods and need to use your gps and maps app, you have to pay for an extra data package, which probably is around 3€ for 200mb of internet. The biggest mobile add on by Vodafone currently is 5GB for their "post-paid" service. They (still) don't have any add ons like the competition, their add ons are for general use. They do however provide unlimited access to some apps (FB, IG, Twitter, Snapchat, Spotify, some extra Youtube GBs) in their under 25 plan which is fucking awesome if you're under 25, however they're charging weekly. So there's months where you pay 4 weeks, and others where you pay 5.
That's pretty much it for now, there's speculation that all companies are going to do the add-on shtick, but regarding home internet, as it has been unlimited for quite some years now, I don't believe we'll have that problem here. Our version of the FCC (ANACOM) is already researching the case of the add ons, we just have to wait and see what comes out of it.