As title suggest..... Yahoo will be closing down it's Site Explorer facility which is used to get details of backlinks for a particular website.
There are many other tools for the same but site explorer was the best among others. Not too sure why they have decided to STOP such a helpful service, let's see if they really take any action on this.
Well, Yahoo site explorer shutting down isn't necessarily the end of the SEO world
They have recommended and are trying to promote Bing and have asked to sign up with Bing Webmaster Tools which seems to be of same quality as that of Site Explorer.