What's your favorite social networking site?

I realize that I am old fashioned when it comes to certain principals. I can't help but to be put off by the idea of Facebook or Twitter or MySpace or any of the other social networking sites. Do I really need to know every little detail of everybody else's life? Do they all need to know what I am doing at all times during the day? Do I really need yet another distraction in my day to keep me from doing the things I need to do or being the person I need to be? Are we losing touch with reality with our relationships? Some might say they are 'closer' to other people because of their participation and some might say they now rarely communicate by traditional means, even email or by phone, now that they are 'Tweeting' and such.

So now I want to hear from you. What is it about the social networking sites you belong to that you have liked or not liked? What are some pros and cons? What are your thoughts on the extent at which you feel you need to be 'plugged in' in order to keep up? What would you change if you could? Do you have any concerns about the reality of your relationships being like disposable gloves in the sense that you don't make as much 1 on 1 contact with those around you? How many minutes or hours would you say you spend a day on these sites? Am I just missing the boat?