Translation: it's for people who (you think) want pretty plots instead of an actual understanding of the data. The article's repudiation of "mullah" (?!) opinion is a little anti-intellectual IMO - these people tend to have a lot of experience and therefore understand common pitfalls better than a lay person's intuition.
Pie charts do not work as intended in general, but may work in specific cases like the one the article shows. Pie charts have low perceived precision because people are bad at estimating radial distances. If in the article's example potatoes were 60 and rice 58, the pie chart would not convey that rice is lower than potatoes - they would look the same. A bar chart or stacked chart does not lose this information because humans perceive location with very high precision. There are several other pie chart failure scenarios, like too many categories, or very imbalanced categories, or very balanced categories. Overall, it's a very non-robust visualization method. It may look good in your presentation now, but when you get updated numbers you may find it becomes a mess.
Yet it's still not great at that. Stacked bar chart (basically an unrolled donut chart) is better - again, because people perceive linear distances with much higher precision than radial:
http://i1.wp.com/flowingdata.com/wp-content/uploads/2008/08/...
Some more specific thoughts:
ALWAYS represent more than one data series if possible: otherwise you're wasting space. But make sure your thesis is still sensible. It's very helpful, for instance, to plot a series of interest against a backdrop of the greater population.
A histogram is NOT the best way to show the average value. A box and whiskers plot shows the average as well as the bulk of the population in a one-dimensional form that can be extended simply for comparison across categories or time.
Also always remember that the data is king. Line smoothing is only a good idea if you're not using it to give the impression that you have more data points than you really do.
All in all their visualizations provide great examples but they could do more to share the nuance that went into designing them.
Personally, I found this very useful:
http://complexdiagrams.com/properties
* this is not a shameless plug!
