The Federal Trade Commission in the US published – as part of a much larger report on privacy – a fascinating chart on the various routes that various kinds of personal information take from the individual to end users of all kinds.
There is a note on the website of the Centre for Democracy and Technology about the chart.
The chart itself is in PDF.
There is a lot of information on the chart, so you will have to blow it up at least to double size to see it clearly (if your eyes are no better than mine…). It . . . [more]