It's not exactly breaking news, but still, it's useful information. The Big 3 have agreed in principle to slightly revise and adopt the Sitemap Protocol that was originally championed by Google. Why does this matter?
The Sitemap Protocol that Google, Yahoo and Microsoft are adopting will further ensure that all relevant pages of a site will be spidered and indexed by their respective search engines. And finally, maybe other players will adopt the standard as well.
Site maps are particularly useful in dynamic sites, ensuring that a site administrator can specifically target any or all pages on a site for inclusion in a search engine.
Incidentally, any site we build has an automatic sitemap generator that regularly alerts the search engines to changes on the site that need to be reindexed.