I just found out that a girl I was pretty good friends with in high school choir died suddenly of a rare form of breast cancer. We had become friends on Facebook a few months ago, and today I realized I hadn't heard anything from or about her in ages. I looked her up in my friends list to link to her page, and she wasn't there. I looked her up in the search box and found her immediately. At some point, she must have unfriended me.
I immediately went from dismayed at her early demise to hurt and angry that we were no longer virtual friends.