Specifically you can see status updates shift wildly from "I'm so happy! My life is awesome!" to "Why can't people just stop talking behind my back!?", often over the course of only a few days.
I get the feeling some people have inadvertently allowed DB to replace their social lives. And FB is replete with empty social promises ("we should hang out sometime"). I can see that resulting in the social mistrust the article's talking about.
When I am on FB too much, I sometimes get the feeling I am looking through a window at social scenes in which I am conspicuously absent. I am sometimes invited to participate, but I can always feel the fake "here's my card" element in the invitations. I don't get that feeling on other social networks --HN, for example--even though I think I have less common ground with the brilliant people here on HN than I do on Facebook. What do you think it is about Facebook, specifically, that creates that feeling?