Google did it again!
With the unsuccessfulness of Wikipedia searchwiki, Google introduced their own searchwiki in Nov 2008. Some of the features were:
1. Users can push websites to the top of search results
2. Users can remove websites from their search results
3. Users can add comments about websites
4. Users can review comments from other users for individual key terms
Users would however need to be logged into Google to use the features. Recently, Google is allowing to share your comments with friends and family without them logging in.
Follow the link for more update on this: Google SearchWiki Gets Social—Kinda