Social reputation
Social reputation, in the context of this project, refers to a process by which the search engine users can describe search items as having certain good or bad qualities. The social nature of the process yields a description that is not just the collection of personal opinions of users but the "opinion of the community of users". A good example of a social reputation based tool is the WOT plugin for Mozilla Firefox.
[edit] Scope
Although the first things that probably come to mind when thinking about social reputation are protection from improper content and pointing out highly recommended content, the scope of the social reputation part of a search engine can be somewhat broader. For example if you "Google up" an error message you got while installing something, the search engine cannot tell which of the pages in which the search phrase appear actually include a good solution for the problem. A social reputation tool can enable users who already found pages with good answers to mark them as "A good answer to <some message text>" so that they will stand out in the results of next similar searches.