Your Breakfast
I keep hearing people complain that Facebook/Twitter/Livejournal/Social Network X just gets used for posting what people had for breakfast. Here's a bit from the article on social networking I'm writing for the SFWA Bulletin detailing ten reasons why I might actually want to know what you had for breakfast.

1. You are a close friend or family member and I am interested in your health.
2. Your breakfast was particularly poetic.
3. Your breakfast was particularly unfamiliar and thus interesting to me.
4. You tried a food I am curious about.
5. You tried something that I know an Interesting Fact about.
6. You had something that has strong emotional resonance for me.
7. You tried something a favorite fictional character eats.
8. Your description persuades me to try something new.
9. Your description warns me off from something I know I won't like. (If you're reliable or I know your taste matches.)
10. I am stalking you. Information like this is a godsend.