All your friends are either having a fantastic time, or their life is ruined. Both can be a bit depressing to watch.If you find it depressing that they're having a "fantastic time", then they aren't your friends in any meaningful sense.
This isn't directed at you. Envy is a stigmatized but natural human emotion. (I rarely feel direct envy, but who doesn't second-guess the path they've taken? It's very easy to look for greener grass and say, "Man, I could be a Director now instead of a 3-failed-startup wash-out", never mind that the other person is Director of a failing, bland company.) Everyone gets down when they see other people having easy, seemingly unearned success-- and oversharers tend to be the hypersocial people who make their successes look even more unearned (it being better, in their view, to be well-liked and socially successful than talented or hard-working).
My point, rather, is that if these people's successes get you down, they aren't friends in any meaningful sense. And social network "friendship" is anything but in many cases, since many people are trying to incite envy to validate their own choices and results.
Most of my real friends I never check on Facebook.