It might also be somehow that these social networks are not attractive to people in the audience who are critical of such stories.

How long do you want to spend on a site debunking stuff? That would not be much fun. Moreover, what would be the effect? Ideally, people would adjust their news filters and start to critical think for themselves. I don't think I've the right educational credentials for that. :-)

Yeah I've thought about that too, people are just being entertained by all the crazy stuff on FB like they would be with National Enquirer.

except National Inquirer was a 2 minute distraction while you stood in line waiting to pay for your groceries, whereas Facebook is a life-dominating addictive habit that displaces higher quality media consumption from the lives of its users.

Some people actually buy that rag.