The concept behind the initiative is to “hide sites to find more of what you want”. It is quite common to do an internet search and get some results that are of no interest to you, using this new feature you can effectively filter these websites out of the search results, therefore having a results page specifically tailored to your wants and needs.
Although anyone that does a Google search will see that there is an option to block a website, the functionality will only work if you are logged into your account.
Although search results will omit the website you have selected to ‘blacklist’ users will be made aware that search results have been adulterated as a result of being blocked.
Once users have blocked a website they are still able to manage the sites they have blocked and will have the option to re-instate if necessary. The new feature is rolling out today on Google.com in English for users with Chrome 9+, IE8+ and Firefox 3.5+. Google have stated that the functionality will soon be available in all languages and regions.
The interesting thing from a SEO perspective is that with the recent Google ‘Panda’ algorithm update that specifically targets content farms and poor content, it is not inconceivable that Google will use this information in the future to affect its search results algorithm.
For example, if a large percentage of users globally block a website this could mean that the content is not useful for searchers. It is only opinion and speculation but I think this is where Google is going with this functionality. The only way to tell for sure however is to wait and see 🙂