What started as an embarrassing hobby (well, it's still a little embarrassing) has become my daily journal of the things I've done and places I've been. Foursquare let me know this week that I've been using the service for four years now, which roughly coincides with my move to Brooklyn.
Between services like Timehop and IFTTT, I've really become locked into the service as a way of tracking my life. What will become of this data, I have no idea - ten years from now I may not care at all what days I went to Bergen Bagels and what days I didn't.
All the same, that much data can make for very pretty infographics!