It appears that Google is now following the example set by Blekko to provide means against search engine spam. The ability to block sites is implemented into the core of Blekko. The functionality is available for everyone independently of the used browser.
Google, on the other hand, limits the ability to block sites to the users of a handful of popular browsers with the exception of (guess what) Safari. Coincidence?
I figure that the feature can only be used in combination with a Google account because otherwise it would be hard to maintain the information about blocked sites across devices. At least, that’s how Blekko’s feature works.
What are we supposed to expect next from Google, slashtags?