It would be like reading an article about what an aspiring engineer needs to know about lower-level systems programming, and then coming across a snippet of bubble sort written in the ugliest Perl you can imagine.
The usual things that are wrong with pie charts:
Ask yourself: How useful would the chart be had the numbers not been provided? Why did he have to give the actual figures? Perhaps because it would be hard to gauge areas? Especially for a 3-D pie chart where you are not looking at it head on. The 25% is not much bigger than the 15% (it should be 66% bigger). And with that projection, it's hard to tell.
In fact, the 25% looks like one fourth of the pie chart - the angle it makes is 90 degrees. That's good and as it should be. Looking at Multivariate calculus and Algorithms combined, it really looks like 90 degrees to me too. But it's not 25%.
What value is added by padding blank spaces between all the slices of the chart? Seriously - how does that help at all? Imagine looking at a pie chart head on (i.e. in 2-D), and then seeing they decided to expand the circle and add spaces. Why?
Now imagine presenting this as a simple bar chart. It would be clearer, and the pie chart shows nothing more than what a simple bar chart would. The bar chart would be less confusing.
Thin font is hard to read
I don't know very much about variations in human color perception, but to me at least, all the colors are clearly distinct (Algorithms&Complexity is a light blue (cyan perhaps), and Others is a sort of pink/purple (magenta perhaps).
> Why is it 3d?
Why not? Don't be so serious!