https://github.com/EFForg/privacybadgerchrome/issues/431#iss...
This looks like it's trying to exercise every dark corner of the user's browser in order to ensure that the browser is a real, eyeball-facing browser and not just a URL fetcher, PhantomJS/SlimerJS, or a clickjacking plugin being used to fraudulently click ads.
I think it's easy to see both sides here: tools like this are a powerful way to detect and combat botnets and click fraud, but if/when weaponized they're also a form of browser fingerprinting which is a nasty way to ruin anonymity across the web.
IMO there are a lot of bigger targets on the Taxonomy of Bad Internet Things: malware-serving bottom-tier ad networks, "wrapped download" sites, clickjacking, and especially cross-site correlative "analytics" companies come to mind as being more sinister to privacy than Dan Kaminsky going botnet hunting.