As stated in Section 2.1, Relevance Feedback is most useful with Exhaustive queries, when a user needs to find more, or often all, relevant documents. However, if a user is simply searching the Web for the answer to some question and any relevant document will do, then there is no real need for Relevance Feedback for Web IR systems. Thus, while Relevance Feedback does help performance for Exhaustive queries, it is an open question what percentage of users have queries that will benefit from feedback.