Of all the different types of data visualisation, maps* seem to have the best reputation. I think people are much less likely to trust a pie chart, for example, than a map. In a sense, this is amazing given that all maps are abstractions from reality. They can never tell the whole truth and are nearly all based on data with some degree of uncertainty that will vary over large geographic areas. An extreme interpretation of this view is that all maps are wrong- in which case we shouldn’t bother making them. A more moderate view (and the one I take) is that maps are never perfect so we need to create and use them responsibly – not making them at all would make us worse off. This responsibility criterion is incredibly important because of the high levels of belief people have in maps. You have to ask: What are the consequences of the map you have made? Now that maps are easier than ever to produce, they risk losing their lofty status as some of the most trusted data visualisations if those making them stop asking themselves this tough question.
Map projections are by far the most common “white lies” told by map makers. If a 3D image of the human body were projected in a similar way it would look unrecognisable and people would say it is an unfair representation of the human form. Far fewer, however, would question the use of the Mercator projection (used by the majority of web-maps) when mapping cases of malaria in spite of the way it shrinks the equatorial regions relative to those closer to the poles. Map projections cannot be avoided but they can be appropriately selected to provide the most reasonable representation of the world for the data being visualised.
Distorting the shape of the world is as old as mapmaking itself and so on its own will not alter people’s trust in the quality of maps as visualisations. It is the data plotted onto the map that has the most potential to do this (especially as it is available at finer and finer spatial scales). Clearly, subject matter is important- if a misleading map depicting whether people prefer ketchup or mustard on their burger was created it may cause a stir in the condiment industry but people (correct me if I am wrong) won’t get too upset if their preferences are mapped incorrectly. If, however, the locations of convicted sex offenders were incorrectly mapped it could have enormous consequences both for the individuals and the areas concerned. I would be happy to create the ketchup vs mustard map (the guys at floatingsheep could probably do it based on tweets) and not worry too much