A group of my students used 5 pie charts to show changes over time in their stat consulting report. Luckily they had some other sensible graphs or it would have been 0 out of 5 for the graphing mark. Worst thing was that it would have been easier to create a line chart than manipulate the 5 pie charts.

Just commenting on the print version.

I think this is a bad example of why pies are bad because here it actually works quite well.
In some ways better than the bumps-style chart.

It is not pie chart by the way but a coxcomb chart.

The coxcombs show relations between sales. The use of area is not too bad as there is some very small and some very small numbers.

The bumps chart show another set of data, the relation of the differences between the sales. The lack of a clear zero baseline is strange and makes this point very clear.

Pies (or coxcombs) and area scale are often bad but no rule without an exception.

@Jörgen - I couldn't disagree more with your assessment.

Whatever you want to call this set up, what we have are 4 bubbles, but all cut into quarters, which takes a poor way of comparing data and makes it harder...

All you can really tell in the print chart is that some numbers are big and some are small. Getting a real idea of how much bigger or how much smaller is very difficult.

The bumps chart makes it very clear how much a value has changed between the time periods in question, and the slopes make it very clear how each category compares to the others in terms of the severity of change.

It also does this at a glance, as opposed to the bubble charts where you need to look at each category, compare it's first and last values, and then move on to the next, trying to keep in mind the first values you were looking at...

I don't see any possible way to defend that as a good way to display the data to the reader.

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