I like to keep my friends list pared down to people I actually care about whatever is going on in their lives. I use FB to keep track of everyone in my life, to know what they’re doing, to check out their photos, and to keep in touch. Those who know me likely do the same for me because I am notoriously bad about not writing or calling.
I have definitely unfriended people, for various reasons. One girl was a crazy Ron Paul fan that kept posting the stupidest, brainless anti-Obama crap after the election. After she persisted in posting repeatedly about Obama’s birth certificate and how he wasn’t born in America and I rebutted with several reputable links, and then she continued to try to argue away reality, I gave up and hit delete. I’ve had enough craziness in my life, thanks.
I’ve defriended exes after the breakup because seeing their updates and how they were blithely carrying on in their lives without me was much too painful. I added them back at a later date, once I’d healed.
One friend who I’ve known for quite a long time tried to scam me out of several thousand dollars and when I called him out on it, never apologized or even commented. Not friends anymore!
I never tell them I’m doing it, I just do it. It’s way more subtle and less like I’m making a point that way.