My group of friends used to call each other on Thursday or Friday nights to organize what was going on. That eventually stopped happening because of facebook. It took quite a bit of peer pressure to get an account and see what the fuss was about.
I used it diligently for about a year to give it a fair trial. I actually liked it until I saw the illusion. I promptly deleted it when I'd had enough.
I found the mediated social experience wasn't adding any value to my life. A lot of friends I had spent a lot of time and energy in building friendships with became casual observers in the stream of events. Instead of being personally invited out with the gang I found that I was just filtering my feed for events and filtering for the ones I would be interested in. I would just get invited to everything because facebook makes it so easy to spam your network. I didn't have to talk to anyone. It was ironically anonymous and passive.
It just didn't work for me. I'm an introvert. I invest a lot of emotional energy in my relationships. I have few friends and I like to shower them with my attention and care. Facebook opened up a lot of opportunities to meet new people and attend parties I would have otherwise never been invited to, but I don't put a lot of value in such things. I'd rather focus on the people that mean a lot to me than to be buzzing about from one event to another and just watching life pass by on a web page.
I'm also of the mind that there are really very few things in life that matter. If some person I barely know in my family just had a kid I wouldn't really care. It never mattered before facebook and it still doesn't matter now. It's just mental noise. I like to take time to reflect and absorb things... too much information just keeps me busy with unimportant things.