I read this article with interest. It showed me a few things which I didn't know about these 3 social networking websites which I used frequently. I daresay Lifehacker got their facts quite right. The image below, courtesy of Lifehacker, shows how the services fare in each category such as privacy issues and usability.
For me, Facebook is used to connect to my entire social network. This includes primary school friends whom I can't even remember how they look like (thank goodness for Facebook), secondary school friends whom I am the closest with and my other friends from Junior College and work place. As long as I see one's name and don't ask "do I know you enough?" or say "I think you pissed me off before" AND the invitation to be a "friend" was initiated by the other party, I will agree to add this "friend". FYI I very rarely invite other people
