Google has recently introduced Digg like buttons and functionality in its Google Experimental Labs.
The experiment allows (opens in new tab) the user to have direct interaction with the results, something that comes straight from Digg's book.
Users can add, move and remove search results which can be made persistent, although Google gives you the opportunity to undo any modifications made previously - provided that you signed in your Google account.
Google adds "like it" and "don't like it" buttons to your search results as well as the possibility of adding your own links.
Google already shows which pages you have previously visited by default and adding promote/demote functions is widely seen as the next step, to complement Google's Pagerank algorithm.
Adding human input will hopefully allow Google to weed out parasitic websites which often pollute results.
There are fears though as to whether hackers and criminals could use this feature to trick Google itself.