I want an option in Google that allows me to say “never bring me to this site again”. The ideal purpose is to avoid those pay for sites which hook on a useful looking domain name and then fill the site with spurious adverts. If I can eliminate those sites from my search them I can give other sites a chance to make it into my search. And lets be clear about this, this is not a per search elimination, I never want to see these sites ever again.
Think of it as an inverted Customised Search Engine.