“StumbleUpon helps you discover and share great websites. As you click Stumble!, we deliver high-quality pages matched to your personal preferences. These pages have been explicitly recommended by your friends or one of 6 million+ other websurfers with interests similar to you. Rating these sites you like () automatically shares them with like-minded people – and helps you discover great sites your friends recommend.
StumbleUpon uses / ratings to form collaborative opinions on website quality. When you stumble, you will only see pages that friends and like-minded stumblers () have recommended. This helps you discover great content you probably wouldn’t find using a search engine.”