I don't have one yet. Yes - I'm that guy with no facebook, no twitter, and only have a LinkedIn account for the Global police to keep track of me.... well except for the TSA trusted traveler and Global Entry fingerprinting I submitted to.
I will have to get one of my kids help me set up one in the next few weeks. I'm kinda afraid to get one. do you have to keep track of all the "tweets" like email? I really dislike email.....