When my mom died earlier this year, I posted someone like "I love you, Mom, and I miss you." I don't know. I felt the need to express something, and I didn't want to say "is bummed because his mom died". Also, most people who know me also knew my mom.
I don't always know the person being spoken of, but when others post something like that, I take it the way I see it intended: as a public expression. Maybe not everyone is comfortable with that, but it just seems weird to me that someone would actually find it aggravating. For most people the whole point of Facebook is to bare yourself. Your thoughts, your likes and dislikes, who your friends are, and the pictures you have of them. I was serious when I said that if seeing that kind of thing pisses you off, then maybe Facebook is not for you.