It'd be cool to see how this was calculated. Though considering the amount of auto-spellcheck and similar that goes on, it's kind of surprising to see that half of the top contributors are human.
The author draws a wonderful parallel between bots in the Wikipedia ecosystem and bacteria in the human body.
And if you want the code + data, you can just xargs https://github.com/lsb/ugc-contributors/blob/master/mh-diffs... over all of your pages-meta-history.7z files from http://dumps.wikimedia.org/enwiki/20110317/ or get the sqlite database from Infochimps from http://www.infochimps.com/datasets/entropy-per-revision-of-w...
You could also just get an outdated version with the work already done for you, here: http://en.wikipedia.org/wiki/Wikipedia:List_of_bots_by_numbe...