It’s a dig, an insult.
The sites can be used in many ways. However, they serve to propagate misinformation more readily than fact.
Plenty of fake news items about “evil republicans” are shared on facebook, twitter, and elsewhere.
Most people are sharing the headlines and not even reading the “news”.
Some of them are from “parody” sites but the low information users there are eating it up.
Example when Wendy Davis huffed and puffed for half a day in the Texas Senate, an article went out that Republicans still managed to pass a bill restricting masturbation.
“OOOOH THOSE EVIL REPUBLICANS!” who cares if it’s even true.
They share the 2-minutes of hate directed at the approved targets. Then they return to bitching about their day and showing pictures of their lunch.
Facebook now even shows you which “topics” are trending so you can join in the pecking party.
That’s more a function of modern media than anything about the nature of social networking. Information just gets around faster these days.