[com2kid]

They may be visually pleasing, but humans just cannot process angular magnitudes at a granular level.

A bar chart where one bar is 25% larger than another is obvious, a pie chart with the same is not obvious. Numeric labels are needed, because the chart itself does not serve as a useful visual reference.

It may look nice, but it does no good. Especially once you have more than a handful of values!

[seanwilson]

My point is making sometimes look good or to draw the eye of the user can be a big enough factor to use a pie chart. Maybe you're only showing two values and only need to convey if one value is larger or a lot larger than another for example.

Not every page is a scientific document.

[com2kid]

If you are comparing 2 values, sure, maybe. But 40% versus 60% still won't be the most obvious thing other than "60% is larger", understanding the magnitude of the difference will involve more thinking, flat out. Taking more mental processing power to understand a visual chart is a bug, not a feature!

[TeMPOraL]

At this point you may as well write it longhand, "X is much larger than Y". Since promoting anything less than maximally accurate beliefs is an act of sabotage on your fellow human beings, you have to ask yourself why are you using a pie chart - because it's not to provide value for users.

[seanwilson]

That's a really extreme way to interpret what I said.