I've asked this question before on Why is the site SharePoint Stack Exchange not to be found using Bing Search?, but was referred to this site:
For some reason I'm unable to find the homepage of SharePoint Stack Exchange using the keywords "SharePoint Stack Exchange".
I'm able to find the Stack Overflow and Stack Exchange sites where SharePoint tags are used. But I cannot seem to find the homepage http://sharepoint.stackexchange.com. Is by any chance the Bing crawler excluded in robots.txt?
The reason I'm posting this is because it's possible new visitors are unable to discover the site if it is not to be found using all search engines.
It would be nice if the site could be found using all (big) search engines.
In the other topic it was found that it is perhaps due to the robots.txt crawler settings for the Yahoo Crawler:
When answering what crawlers do and doesn't do, one is out on thin ice. But you have a point that the start page doesn't show up in the 154 results of your search string on Bing.com.
Facts are that the robots.txt file disallow all crawling from Yahoo! With the comment saying
# Yahoo bot is evil.
Now, we know that Bing and Yahoo have a ten year agreement tocooperate in search applications, than there might be a possibility that they share crawl results with each other. If so, and the Yahoo crawler Slurp visits SP.SE it actually follows the robots.txt and shares its non existing result with Bing.
But this is just a qualified guess, where we need to talk to SEO-guys about it, or maybe follow up your question on Meta.SE!
Good catch though!