There's a cell/mobile service over here that's advertised as "Unlimited Social Media". So customers get limited data but "Social Media" data is unlimited. Exactly what they define as "Social Media", I don't know. (Does my blog count?)
That's a curious business model. Why does an Internet Service Provider want to prioritise one particular class of website?
Probably because social media use is easy to model and a relatively tight distribution, from a bandwidth perspective. The more targeted your pricing tiers, the more you can compete on price without taking a beating from top talkers.
Nobody wants to service the top residential users because they cause way more traffic and trouble, but it's probably hard to fire individual customers in most places. It's like zoning in that way. Nobody cares if I have chickens in my backyard, but it's illegal because 15 years ago someone's neighbor had 20 chickens and a few roosters, and the neighbor got a law passed rather than resolving it with the neighbor.
That's a curious business model. Why does an Internet Service Provider want to prioritise one particular class of website?