Earlier today I saw a video about Facebook's Open Graph (Deep look at Facebook's Open Graph (enables "frictionless sharing")), in which there was a lot of information about Timelines. I'm not a fan of Facebook for many reasons, and I'm not suggesting Google+ has Timelines, however I do like the idea of being able to look back and remember what I was interested in at different stages in my life.
The video explained how apps on your phone and computer can tell Facebook about the articles you read, the music you listen to, the videos you watch, etc. Facebook will then make a Timeline in which you can see interesting data like when you discovered a particular show, when you discovered your new favourite band, how often you listen to certain tracks, etc.
I don't like the idea of every song I play and every video I watch being posted to my Stream, or the privacy issues involved with sending off every single activity I do in my daily life to a 3rd party. But I do want to know things like "When did I discover that show? What was my favourite band at that point in my life? At this particular time, what was I interested in?"
I'm not sure there is a realistic and idealistic way of doing this without making a diary or something, which is a shame. Maybe I'm just sentimental, but I would find these statistics and memories very interesting to look back on over a period of time.