I had to go through the slides to understand this: basically, it said in the case of a woman they did research on, she commented and liked photos of her friends at the gay bar, but her ten-year-old students could see those comments too. The thesis was that a bunch of her social groups that shouldn't interact were forced to interact on Facebook.
Now that that's overwith (if you were as confused as I was), how does Diaspora solve this? I'm honestly asking. Do you not see updates on another service, or something?