The ad-block thing is where I first saw it, that and DRM for less-than-legal sites to prevent downloading (stops streaming if the dev console is open)

I mean more specifically taking advantage of the awkward UI to cover up your tracks on local storage, it's something that's just devious enough that if you get caught (which is not difficult) it'll be hard to explain what you were doing, and you'll be trying to explain it to technical people