Another area where multiple sets of data for what is the same thing cause confusion is how temperature is visualised on the BBC weather maps, they display from one set of data (ie temperature in towns and cities), and then often speak of temperatures from another set (in the countryside) you aren't privvy to see.

I am very cynical how statistics are used not to clarify but to confuse, so if someone complains that you didn't get the temperature right last night it was far colder.. Argh that's because you were looking at the temperature in towns and cities!