Its the domain which is responsible for this. Just for your domain name without the extension, it will return the results with your domain at the top. And, it can also be beaten with proper SEO and Link Building.
The last Google update to avoid Google Bombs, was not to allow any website to rank if the required keyword is not listed some where on that particular page meta-tags or content, however i have seen some cases few sites ranking for some keywords but after a deep research i figured out that they was using domain redirections to get their results Pretty well wear but it's all about back links, what do you expect from a PR 10 website like Google.com ??