Google announced this week that they are testing a button functionality similar to Facebook’s “like” button. Known as “+1”, the button is only available to Google profile/Gmail users. This button gives users the ability to show their approval for search result relevance. The button appears when you are logged-in to your account, next to any search result.
While pushing the button, you will give a stamp to the search result that will be indexed more highly when linked friends perform the same search. Is like voting for a web-page or a web-site. It appears that votes are not limited to only immediate connections. Actually, the votes are public and can appear in any search result.
At the moment this feature is only experimental but will appear in more places as the feature grows.
If you want to enter the experiment, check Google Labs.