Old fashioned detective work is expensive and labor-intensive. Which means it will be only used when there's really something at stake. Also, your contacts migh

Old fashioned detective work is expensive and labor-intensive. Which means it will be only used when there's really something at stake. Also, your contacts might tell you that they were interrogated later on. It is visible. Data mining is different because it can be used against everyone at the same time, and because it is completely invisible. This has never been possible in the past, at least not at this scale.