I'll use myself for example. I'm not particularly prone to sharing or to envy (at least, that's what I thought). I rarely posted anything to Facebook, and when I did, it was science or news related. I even felt violated when others posted pictures of me. However, after about two years worth of Facebook use, mostly lurking, I was surprised to find that I was angry with just about all of my "friends." It seemed they were so much happier than me, wittier, more liked, more photogenic. Their families seemed so perfect, while mine was in smoldering ruins due to tragedy, divorce, and bitter grudges. Their posts got loads of likes and comments, while mine received few or none. They also seemed, well, so dumb: they wrote "are" for "our" and mixed up "they're," "their," "and "there." And they broadcast inane political rants, which, turns out, is a great way to ensure that I'll never want to hang out with them again.
So, in turn, for me at least, I found it had affected me negatively, so I quit using Facebook, and I think it made me much happier and a better friend. I stopped placing expectations upon my life by what I had seen on Facebook. And, most of all, I was shocked to discover how judgmental I had been toward these people. I'm the guy who is often jokingly referred to as the family shrink. Everyone comes to me with problems because I'm patient, I listen, and I don't judge. Well, on Facebook, I was a different person. I was brutal. And that attitude alienated me because I found that I couldn't like people in real life whom I couldn't respect in digital life, whether it be due to my own selfishness or their poor grammar. Perhaps that's why I rarely posted—I felt that I would be judged just as I had judged them, and I feared rejection.
Now when I talk to my friends, they seemed shocked that they have to fill me in on things that have been thoroughly covered on Facebook. But when we do talk, it isn't infused with the expectation to please. I can be honest, and so can they, and there's no need to feel like we're having a loud conversation while sitting at the center table in a crowded restaurant.
I don't think this applies to everyone. I have a friend who doesn't seem the least bit bothered by this. Maybe I'm emotionally weak, or overly sensitive, or more prone to envy than I would like to think. And I don't condemn Facebook entirely. Like you said, I think we're still working this whole thing out, and we have yet to figure out how to positively integrate it into our lives. Even so, I think for some people, no amount of sharing is good, not if we're only sharing the good bits.
Sure, I miss finding out about some weird events, but generally speaking it means I communicate directly with a subset of friends I care about rather than all-and-sundry.
I was going to write "...and it makes life more meaningful", but that's false. Actually I sometimes scratch my head in wonder .. what are all these people doing?
Yet that feeling has existed since childhood and I have come to recognize it as a part of me, part of what makes me different and strong.
Never give up on your own perspective. Be honest to yourself.
Let the sheep graze and fear not, for others also tread their own path.
If they find value in telling each other about their life experiences but you don't, that's fine. Maybe they enjoy seeing the cool things their friends do, maybe those posts give them great ideas for vacations or what to make for dinner or what kind of dog they want to get.
You can leave the "yeah, what sheep" bullshit for a t-shirt at Hot Topic, where it belongs.
So I quit. I have been happier without it.
I call, text and email my friends more often. I meditate far more often. I keep a diary. Friends know that I quit and tell me when something is posted that I should know about.
Last night I went to an Eric Clapton concert. My friend repeatedly used her camera, zoomed in and out, took lots of pictures, even curated her photos during the show itself. For much of the evening, it felt like I was there by myself. So I did what any reasonable person would have done: I gave myself over to the music and danced.
But it is a very interesting overall trend and could have serious impact on depression or anxiety, especially to people already predisposed to that sort of sensitivity. You're absolutely right, it's something we need to watch out for.