I stopped using Facebook about eight years ago. I just became uncomfortable with people I hadn't seen in years were getting in touch. Many of those friendships ended for a reason. An ex of mine didn't try to get in touch directly but added friends we had in common - and even tried to friend a member of my family. That was my "fuck this," point.

As for Twitter, it was useful as a sort of social texting tool for myself and friends. About 2-3 years later the celebrties, journalists, politicians and trolls arrived, and it turned into a completely different kind of product. People began using it differently. It no longer had a purpose for me... so I dumped it.

I deleted a Reddit account a couple of years ago (it was probably about seven years old) after someone I fell out with exhaustively researched me and obtained my phone number. It took several months for me to regret it. Reddit is one of the few 'social' sites on the internet I find genuinely useful. It's a sort of web-based Usenet-lite of modern times.