Yahoo Inc. unveiled a service Wednesday that allows users to get their questions answered online for free by volunteers. The feature, called Yahoo Answers, gives a human touch to what has typically been the exclusive role of the Web portal's search engine. Users can submit questions on any topic at answers.yahoo.com and wait for others to post responses, sort of like a community reference desk. To flag inaccuracies, individuals can rate the responses based on quality. Ofer Shaked, director of engineering for Yahoo in Sunnyvale, said that the goal is for users to share knowledge, much like they already share photos and opinions within the Web site's Flickr photo-sharing service and Groups areas. Some users may even gain a reputation as experts on certain topics based on their highly rated answers.