Useful, simple and gives a very good summary/summary on headed pages Rated 4 out of 5 stars
I use it some months now and must say, its great to know all the sites which want to crawl into my browsers cache (and maybe somewhere else)!
The placeholders for i.e. images are great. If you hover over a placeholder, you can read the source of the image and then decide to switch that site on in the preferences very quickly.
I'm only missing a sync feature. Im-/Exporting is possible though, but I'm working with my MAC the whole day and after work its very inconvenient/time-consuming to export and import the black- or whitelist to my PC
Beside this, its a great addon and its greatly helps users to get a clue whats "behind" the page, they're surfing!