Part of creating a good visualization involves knowing a bad visualization when you see one.
While style is subjective, some visualizations cannot avoid leaving the viewer befuddled. Here’s one example:
GE (data sourced from BP’s Statistical Review of World Energy, June 2010)
The only way to understand “Gas Giants” is by reading the text - the graphics lend nothing to understanding. Differing size boxes distort the comparison between countries. The chart intends to measure percentage of gas reserves within a country - one data dimension. Yet, the graphic changes across two dimensions (height and width). Naturally, the mind attempts to compare volume - but this is a more difficult comparison to make. Any comparison that could be made is confused by the arrangement of the boxes. The white space in the lower right-hand corner leaves the viewer wondering if the designer made a mistake.
In the end, the viewer must read the numbers to have any idea what the visualization attempts to communicate. Since the viewer cannot understand the graphic without reading the numbers - a simple bar chart or list of numbers would have presented the information much more clearly.