Social media is the new smoking. Cancer destroys you physically but these sites destroy your mental health. Not just Facebook but Instagram too for example, it's even worse. And don't forget Twitter.
That's just absurd. Maybe people with underlying psychological issues are somehow damaged by Facebook, but in my experience the majority of users (at the very least the people I know who use it) just see it as a convenient way to keep up with what friends are up to and share interesting jokes/memes, it's certainly not destroying their mental health. If someone suffers when they see other people doing well, because th…
It's a distraction. And a lot of people are addicted by it, so much they feel they need to "share" what they are doing or what they are thinking at least once a day. This focus on the Self and the ubiquity of social networks makes for a phenomenon that did not exist before.
As for whether it is positive or negative, well it's a net loss of time (and mental attention since social networks tend to disrupt you the whole time with notifications) that could be spent somewhere else, and it's difficult to argue with that. Are there emotional benefits? Sure. Are such benefits more rewarding than the ones you would get from real-life networking and real-life activities? That should be the proper benchmark to use to make a judgment.
For people who have lived before social networks existed, such evaluation could take the form of a simple question "has Facebook made your life any better?".