It looks like there's a tipping point, when the happy awesome things that your friends are posting starting getting to you, making you sad that your life is a colossal disappointment. That tipping point is at 354 friends:
Among the group who read updates, the study revealed that having 354 Facebook friends seemed to be the tipping point after which people were increasingly less happy with their lives.
The reason: Much of how we judge our success in life is based on how we stack up against our peers. “The problem is that Facebook gives us a limited view of our friends’ lives, and that view tends to be unrealistically positive,” says study author Dilney Goncalves, Ph.D., a marketing professor at IE Business School in Madrid. The more friends you have, he adds, the more likely you are to spend your day enviously reading about someone’s paradise vacation, new girlfriend, or job promotion.
Tough luck to the 141 "friends" I'll be disposing of (virtually) today. No more social media imposed depression for me.