Haven't you ever looked at a map where all bigger cities were highlighted because they had the highest occurences of X (for example burglaries)? It happens very often that populations are not taken into account rendering a visualization less informative.
Today I saw a visualization in Mary Meekes (Kleiner Perkins) well-received slide deck on Internet Trends.
On this slide you see North America and Asia doing very well, both accounting for almost 30% of online learners. I added the graph 'Population by Geography' below and it shows a clear population difference: North America 8% vs Asia 60% of the world population. This means Asia isn't doing that well as it's population is over 7 times bigger than that of North America!
Whole 294(!) page slide deck, well worth your time: