I hate social networking sites... (A seasonal message from Thomas Jefferson)

It's interesting to me that I caught this thread because I am currently receiving some small pressure from two people "to facebook" (it's interesting all by itself that this has apparently turned into a verb). I am not a current member of facebook or any other social networking site. I see it like most other aspects of the internet -potentially useful, potentially a waste of time, potentially abusive. Someone told me recently that intermittently there are "defriending" days. Could that be true? Why wouldn't you just cut them off when ever you wanted? I don't get it. Also, as I undestand it, you can be just as anonymous as you want to be so I don't see the concern for overexposure. But I've never done it so I don't really know.