I blame it on what I call Zuckerberg's Bubble -- not a reference to the current (and rapidly deflating, thanks to FB's IPO) tech bubble, but to the social bubble Zuckerberg has been living in since his Harvard dorm-room days, when he started monomaniacally coding Facebook into existence. When you're in college, and still trying to figure out your identity, you're almost hardwired to **feel like you're being left out **(especially if you're a nerd) of all the coolest stuff that's going on, both on and off campus. So you convince yourself that you actually care what all your friends and acquaintances are doing at all times.
So cool kids have too much attention paid to them anyway, so they can afford to (or even have to be be) more aloof and not “share” much. OTOH geeks and nerds and Zuckerbergs are obsessed with the sharing game as they desperately crave attention in their lonely worlds. This is why Facebook was created. Interesting.