Peter Dreyer in Future Now advocates for a flickr-like website for personal maps.

Imagine if we all gave up some of our right to privacy and produced and shared dynamical private maps. Not just maps of the local neighbourhood, but maps containing information about when we had been where. Pretty straightforward. It would no longer be left to Hollywood to speculate in what would have happened, if I had taken another route to the office this morning - or if I had been 10 minutes late. On the map sharing server (Mapr?) some pattern recognition routine would allow me to see, who I would have met in that case. It would even be possible to perform match making among persons travelling in my foot steps but at different times. People I may otherwise never have met would suddenly leave anonymity. As in the movies our lifes would begin to converge.

Some interesting data-mining could indeed be done... but it raises huge privacy issues...