Starting last year we have been transitioning the backend for our organic search to the Microsoft search platform as part of the Yahoo! & Microsoft Search Alliance. The transition of algorithmic search results for Yahoo! Search result pages is complete for US, Canada, Australia, Brazil and Mexico. We plan to transition the rest of world markets later this year.In an August 2010 blog post, we said we would continue Site Explorer with a focus on new features for webmaster community, even after the transition to Microsoft platforms is complete. We listened to your feedback, and along with the team from Bing Webmaster Center looked jointly at the roadmap for the webmaster tools. Having two webmaster portals for a single source for organic results does not add enough value. Once organic results are transitioned to Bing in all the markets, we plan to shut down Yahoo! Site Explorerand Microsoft’s Webmaster Tools will be the source for Bing and Yahoo! webmaster site and analytics data.
The Bing Webmaster Center team has been actively adding new features over the past few months, including detailed traffic statistics and a new inbound links feature. Microsoft is also committed to build analytic reports that include Yahoo! search usage. Further details on these reports will be coming soon. You might have some questions that we will try to answer below:
Microsoft Webmaster Tools to support Yahoo! Site Explorer Community

I think it is a good thing that Yahoo site explorer shut down, it should be more private so spammers cannot sniff your backlinks.