This is something I think about often when it comes to tools. The idea that Google had all of my location history for the past 8 years means I can see everywhere I've ever gone. I can lookup any email I've ever sent/received. I can look through my browser history for any particular day. With Spotify + Last.fm I can see stats about my listening history, and with Tract.tv I can see my TV/movie watching habits. Strava tracks exercise, and YNAB tracks budgeting/spending. There's an incredible amount of health data from my iPhone + Apple Watch.

It's really cool to think that all of this data exists, but I'm not really sure that it's useful. Occasionally I've gone back through my old search history for that one old post that I wanted to re-read, or go through my Spotify listening history to find a song I really enjoyed but forgot the name of, but 99% of that data goes to waste.

Quantified Self [0] is an interesting project to me since it seems to make use of data from all of these disparate sources, but I'm still not sure what the outcome of tracking all of this data is. It seems cool but not useful.

[0]: https://quantifiedself.com/