I've had a personal policy to not join any social networks. At first, I didn't understand why I would want to post updates about my life on some commercial web site. I had my own web site, so why did I need Facebook? Now I see the appeal, but they still aren't for me: I don't want to manage yet another online information source in my spare time. It's nice that my wife is basically on every social network, so I get my updates through her. Not so secretly, I think this is actually ideal: I don't do anything, and I still see most of the interesting things my friends post. However, I've also long believed that it is important to promote your own identity online, which is part of the reason I have a personal web site. Today, I'm willing to admit that online audiences have changed, and if I want to reach them, I need to be on social networks. In particular, I'm now involved in a startup that I need to promote, so I need to be less idealistic and go where I can reach the right people. As a result: I'm sad to announce that I now have a Twitter account, a LinkedIn profile, an AngelList profile, and of course a GitHub account. I guess you can contact me through those things, but I really would just prefer an email.
Having recently signed up for all of these, LinkedIn is particularly sleazy during their sign up process. They imply that you need to give them your email password and post their advertisement on your Facebook page. Gross.