Dot maps, if properly created, can be easy for the viewer to understand the data that is being represented. A dot map not only shows the density of the phenomenon but also the relative location so trending can be seen.
On the other hand, dot maps can easily become so cluttered that the data becomes unusable. If dot values are to small greater accuracy will be perceived by the viewer. Using larger dots only a small number will show on the map and any pattern may not be visible. Without the use of computers, dot maps can be very hard create with any amount of accuracy and it is hard to estimate density with a dot map. Dot maps should also not be used when making large scale maps.