Dave Winer discovered a new Google interface experiment: every search result has a small arrow on the left. If you click on that arrow, you get more information from that site: relevant images, an extended snippet, facts and a search box that allows you to restrict your search to that site.
This experiment proves that Google tries to deliver the answer for user's query, so the user doesn't have to visit the site to find the answer. Eventually, when search engines will become really smart, they'll be able to provide a page compiled from many sources that tries to respond to a query. You'll visit the sources only if you need more information, and that's not going to happen often.
Yahoo Instant Search
Check the new Google design
New Yahoo homepage