Regarding Twitter, I've seen tons of abuse on there, which is normally as already observed by others to be the sort you wouldn't tolerate face to face. I was going to put that far more bluntly mind!
I do love Twitter though I don't live on there. You might not think that if you follow my Live Trip Reports on there when I'm on a trip, some trips I'm tweeting at least 40 times a day! For the majority of time though, I keep a fairly low presence on there, using it more while bored and curious as to what's going on throughout the country on the railway.
Which incidentally is what I was first using Twitter for, contacting TOCs with questions. It eventually grew on me, after a couple of weeks I got more and more used to it and loved it.
Facebook, well you'd think it was the centre of the universe, that the world revolves it judged by typical conversations at work. They all moan about how there's never anything interesting on there, yet they all still flick through their news feeds all the time. If you don't know about X happening, you'll get "It was on Facebook", or "According to Facebook Y is here for Z months". Then there's "making things Facebook official", as if you have to get their permission before leaving a job, getting engaged etc. :roll:
Of course, there's all the other nonsense people have mentioned like the attention seeking brigade, the food bloggers and so on there too. I got bored silly of people posting non-stop about their kids, with what felt like a million photos a minute being posted. The entire news feed was getting filled to the brim with nonsense I had zero interest in, but for the sake of unity and keeping the peace I didn't dare block or delete the work people doing so. I tried dealing with it by adding as much train stuff as I could to pop up in my news feed, but it was almost like looking for a needle in a haystack with all the nonsense from the veg (in this case, non-rail heads) so I simply got bored of it. I went 48 hours happily without using it, and in that time I'd right royally fallen in love with Twitter.
So it wasn't hard whatsoever to leave Facebook, I've been off there since late January 2015. I had to log in once a few weeks ago to click on accept on a friend's birthday bash, in an attempt to get others to say they were going too, but I reinforced that with another post to say that I wasn't back and where they could find me.
Anyway, as for Twitter, if you ignore the idiots and use it sensibly there's no problems. I do use it for sending positive stuff to TOCs via Twitter if I've had a good journey (not always mind, after all the same thing all the time would get a bit dull), or if there's an issue that needs reporting (no working lavatories, that sort of thing) then a quick tweet goes off.