I don't think this would ever be as granular as allowing/slowing down access to specific websites, although I'm not sure about the likes of Facebook or Twitter, as I know from experience they consume a lot of traffic - but none of them are even close to Google. I think the vast majority of internet content will remain best-effort, simply because it would be too difficult to price/police.
It's always going to come down to the content providers, Youtube, Netflix, etc, along with stuff like online gaming - Blizzard, League of legends, and other big online games etc - all of which could be broken quite easily by an ISP in return for payment, by provider or customers.
The difference is that in some cases consumers may be better off - because you can bet your bottom dollar that these companies will pay off the ISPs to guarantee consumers access to their products.
Content providers and online gaming companies know that customer/player experience has to be at the heart of what they do - and they spent enormous amounts of money making sure their stuff works properly, in the wake of an ISP throttling/reducing access to their content - that's a direct risk that could seriously hurt them, so they'll simply pay - that could mean that their traffic is elevated from the best-effort class it currently sits in today, to an elevated class for paid content, which could equate to a better overall experience.
Is it right / wrong / fair / unfair? I think on balance it's probably unfair - because it's an easy way for an ISP to create a revenue stream by grabbing big providers and/or customers by the balls and saying "pay for access or die" when customers already pay the ISP for access to the network with their monthly charges, to me - it's an easy way to just make more money.