I like a lot such analyses based on the network structure (not long ago I made something similar for Stack Exchange - http://stared.github.io/tagoverflow/; continuation of my older one https://github.com/stared/tag-graph-map-of-stackexchange/wik...).

Though, technology-wise, it is one use-case where SVG beats pixel graphics, both in terms of usability and interface (whether it is custom D3.js or something graph-oriented as http://sigmajs.org/).