I "got" facebook in 2005 as a freshman in college, and deleted (not deactivated) my account in early 2009, as an experiment, and have been off ever since. I wanted to see if it would have a positive or negative effect on my social life.
1000% positive.
Now, if I want to know about one of my friends, I call them, text them, email them, or hang out with them. If someone wants to communicate with me, they do the same. I get texts all the time that start similar to "hey, facebook-challenged friend, theres X going on next weekend, come hang" or a phonecall/email saying the same, which leads into actual personal communication.
People might call it selfish, but my response would be: why am I obligated to use facebook to organize my social interactions? I don't make anyone contact me, and if they don't want to, they won't.
Also, I became really sick of baby pictures.