What's a friend on MySpace, Facebook, and Orkut? If you have five hundred friends, are they really friends? These are the main reasons why I have not, to this point, joined any of those sites. I don't have many friends, because I just can't give a lot of people the energy needed to maintain a true, lasting friendship.
What does this have to do with technology? Well, Facebook Connect and Google FriendConnect are two apis, with many more to come, that allow you to take your social graph with you. So now, instead of just being a bunch of people that post something they copy and pasted onto your "wall" at major holidays, they are now people who are going to affect recommendations you get on other websites.
Tell me, do you want five hundred of your "closest" friends opinions, tastes, and web surfing habits to have a direct effect on your web experience?