Recently there has been some concern at various forums about the use of Open Director Project (DMOZ.org) web page descriptions by some search engines as the default description used in the search engine result page listings. Simply put, if your web page is listed in ODP, the search engine may choose to use the description of that listing in its results, since they were approved by a human and are most likely accurate.
The problem is that many people have ODP listings that are outdated, and therefore do not match up nicely with the new page content. ODP is notoriously slow in responding to requests by webmasters to modify listings, so the idea came about to create a new snippet of code that would direct search engine spiders to not use the ODP description when indexing a page. Barry posted at SEW Blog today that Google is now joining MSN in recognizing the new "No-ODP" (NOODP) request.
Google has more information on this development at their Inside Google SiteMaps Blog, and the discussion is just getting started at Search Engine Watch Forums. Also see discussion when MSN implemented this in may at High Rankings Forums.
