All looked good, but as it includes more than just banner advertisers (shock sites, tracking sites - privacy issues) he'd have more false positives than I did.
Ghostery and the like (browser plugins) are reasonably easy to just disable when you come across an instance that it breaks functionality in a web page. But using a hosts file or DNS block, it was much more opaque about why it was failing as you'd have to remember something you'd forgotten about: You've blocked this thing at the DNS level, it wouldn't resolve. Or more to the point, it would resolve to a local web server that served up zero bytes.
That's my worry with a black box on the line... how easy is it to override in those edge cases, and will they play safe by sticking just to known banner adverts and not tracking sites which are sometimes necessary parts of functionality (due to the fact that links are redirected via the tracking site).
But that won't catch everything.