A few minutes later "I" posted several Tweets about things I knew nothing about. OK, I suppose there's nothing new in that! But the fact is, it was not me who was Tweeting this stuff. My Twitter account had been compromised, accessed, hacked.
I left Facebook because of what I would call it's "hidden openness" - meaning that it was not always entirely obvious that almost anybody can jump from 'friend' to 'friend' and find out all sorts of stuff.
Things seemed a little better on Twitter, where you could block people from seeing your Tweets, and not receive theirs. But in the end, social networking sites seem to be ripe hunting grounds for the scumbags and low-lifes that invade the internet for all sorts of reasons, from what they consider fun, through nuisance to criminal. I don't think I'll be joining another "social network" any time soon so I'm afraid I have to say to Twitter, "I'm out."