Stone Temple Consulting's Eric Enge has posted a transcript of an interview with Tim Mayer, the person responsible for the product direction of Yahoo! Search Technology.

Tim Mayer opens up with Eric in the interview and talks about Yahoo! Search Builder a search tool which resembles the Google Co-op. He talks about a feature of the search tool, visible tag cloud.
 
It's a user interface that goes very well with the social search initiatives as well with Web 2.0. It provides the visitor to the site some ideas about what other people in the community are searching for and what's "popping". I think it will also drive more traffic because people will see interesting topics that may be timely or may be popular, causing them to click on it and initiate a search. Often times when users aren't familiar with a topic they won't know what terms to search on. So this can give them an idea of things to search for - they may say "that sounds interesting" or "I'd like to learn about that". This leverages the expertise of the community to help the user learn about a specific topic.

He also tells Enge that Search Builder valuate the site and perform a deeper crawl of it.

What it does is to evaluate your site and potentially perform a deeper crawl of your site. For example a lot of people want to create site search. With that, you want a comprehensive search of the site. Sometimes the site is fairly well indexed. What we're saying is if you use Search Builder, we'll potentially include more of your documents into our index.

To get more insight into Yahoo! Search Builder, read the complete interview.