This is truly mind blowing, on the surface, MyWeb 2.0 is basic. Its probably first best that you read Chris Sherman's write up on the concepts of this feature, his article is named Yahoo Integrates Personal & Social Search with MyWeb 2.0. But you don't realize what is meant by "Social Search" until you login. What I mean by that is I see my Yahoo! 360 social community's Web searches. The following image is called "My Community's Tags", look at it!
In terms of how this will change search, Chris Sherman sums it up well:
Yahoo has also developed a new relevance algorithm called "MyRank" for MyWeb 2.0. "It's a new search engine that we wrote that can search across thousands of nodes and millions of pages in a trust network," said Walther. Unlike PageRank and other link analysis techniques used by general-purpose search engines, MyRank is designed to ferret out clues to relevance based on the pages you and your community have saved to MyWeb 2.0.
In practice, this means your search results with MyWeb 2.0 will be very different than those you get with Yahoo, Google or any other major engine. It also means that your search results will change over time, as your personal web and those of your community expand. Walther says these changes should lead to more relevant resultsóbut that depends largely on the "quality" of members of your community and the web pages they choose to add to your communal web.