Stylometry is a really cool field.

For example it was used to figure out if a subreddit was being manipulated by a small number of sock puppet accounts: https://www.reddit.com/r/Bitcoin/comments/3hf5z7/determining... https://www.reddit.com/r/Bitcoin/comments/3dszzu/55_btc_boun...

(and of course the people studying it the most are the ones hunting for satoshi =P)