Yesterday, we reported findings that MSN was returning Google AdWords links in their natural search results. Well, Microsoft has responded to this issue on the Live Search Webmaster Central Blog, explaining that it was a complete accident and that it will be fixed in the upcoming days:
The issue stems from the way Live Search handles content disallowed by the Robots.txt file. We regularly check the robots.txt file of a site to ensure that we don't index and cache pages excluded by the webmaster. However, if we do find a link elsewhere on the web pointing to a page excluded by the robots.txt file, we may include the link and the anchor text in our index if we think it might be valuable to our users. Yesterday we accidently began including the links from the ads of Google AdSense customers. The issue has been fixed, and you should see the results disappear from our search results over the next couple days.
Vanessa Fox at Search Engine Land explains a little more about this and explains it's primarily due to a new way the Google renders AdSense units, a claim that is neither detailed on Google or Microsoft's side. However, much thanks to Microsoft for responding!
In fact, the problem does seem to be resolved. Try searching for confirmation: http://search.msn.com/results.aspx?q=site:www.google.com/pagead. Thanks for the fast turnaround, Microsoft!
Forum discussion continues at Sphinn.