Normally when you take down a page at one URL and then put it back up at an other URL, you use a 301 redirect to tell the search engines that the page has been permanently moved to a new address. A 301 redirect as defined by the W3.org is just that, a permanent redirect. Google and other popular search engines tell all Webmasters to use this technique when moving pages.
Yahoo! on the other hand tells people to create a page that says, this page has been moved here. What Yahoo is telling you to do is create a "doorway" page. Most of us know that doorway pages are SEO No Nos. So for Yahoo! to tell its SiteMatch customer to generate doorway pages instead of using a 301 redirect, is just not right. Those doorway pages can run the site owner the risk of getting penalized by Google and other search engines.
This leaves the Webmaster in a tight position. If they stick with the 301 redirect, Yahoo will treat it as duplicate content. If they switch to the doorway page all the other engines will treat it as a doorway page.
The standard for page relocation notification has been 301 redirects. Yahoo!, like all other search engines, need to support this standard.