Maybe you don't, but what about you and the sum of your friends and friends of your friends? That doesn't just mean tagging pictures or facial recognition - that includes collating ips and times - in someone checks into Starbucks with a NATed ipv4 ip from Starbucks wlan and your visit fb from the same external ip...
A lot of people do multiple post a day on facebook and use it as their only private messaging solution, it's as close as you can get to having your whole life archived on the internet.
