Scour is a search tool that blends results from Google, Yahoo, and MSN together in one stream. You can hot-swap between the three, or break out any single result into another search. If you come across a bad result, or one you think should go above the others, you can also vote it up (or down) or leave a comment.
Unlike traditional search engines, Scour also has something called Friends Feed, which keeps track of friends on the service and tells you what results they are commenting on. It also allows users to add an image to their profile, redeem points through the user administration pane, and edit the number of results returned from each engine to match searching preferences. Further, the service rewards users with gift cards for searching, voting, and commenting on good results; doling out points for each user action.
While controversial--and disruptive--the idea of giving users the power to edit search results has become a popular new feature on more mainstream search engines, including Google, which added it in late 2008. Scour's longevity lies in blending the results from multiple search engines, and rewarding users who help make them better. A growing number of people seem to be quite keen on the idea, though it's certainly not for everyone.