The Facebook UNfriending

So trying to figure out when it’s ok to un-friend someone on facebook. How long do you have to go without speaking before you’re not friendly enough to be on someone’s list? I think I’ve only ever unfriended 3 people and all of them were people I either had never met in person or had only met once or twice through someone else who I rarely spoke to. I always just feel so guilty. Like today I saw an old high school friend in a picture in someone else’s album and was thinking that I hadn’t seen any pictures of her wedding that last time I’d seen her status update she had been planning for the summer. So I clicked on her profile only to see that I had been unfriended. I sat here wondering if I had done something to piss her off or to upset a friend of hers. Spent 20 minutes trying to figure it out when I realized that I hadn’t spoken to her since last winter and that’s probably all it was. Wow, I’m a bad friend that I can’t talk to all my 500 facebook friends on a regular basis. When is it ok to unfriend someone? Am I the only one that gets hurt and offended by this? Yeah, think I worry too much!