Oh, I'm well aware. In Australia, I remember seeing a number of the telcos advertising "mobile data with free access to facebook and twitter". One of the catchup TV services also has "unmetered access" deals with a number of ISPs.
I don't think that the world is going to end here, or collapse into some dystopian nightmare, but the question was asked: "what are these bad precedents?" and I attempted to answer.
Facebook already does this https://www.facebook.com/notes/facebook/fast-and-free-facebo... and I'm sure many others do as well