Here’s an interesting example of what a huge wake we leave behind as we move thru modern life. The CIA team that kidnapped a guy in Italy and sent him off to Egypt to be “interrogated” left behind a nearly complete record of their movements (down to a few feet) and contacts. They left their cell phones on and since modern cell systems track and record everybody’s movements the Italians only had to get a court order and a database query. There is an unbelievable amount of casual revealing about you that your totally unconscious of.
A few years back the Irish cellphone company discovered that they had neglected to discard ten years of this data. Traces of every cell phone user in Ireland for a decade! Kinda puts to shame the data set MIT collected recently. They got a 100 volunteers and recorded 40 years of data (i.e. a couple months each). But you can download large swaths of their data and they have been doing some really fun things; like discovering who your real friends are and where your likely to be next tuesday at 6:45pm.