I am quite amazed that domain name is so important to display relevent ads. I have a site, about freehosting service, but my domain name includes the word "book", a lot of contents ads are about book, such as self publishing, you should write a book, proofreading, ebook, buy a book from amazon, etc. I think I need register many domain names.
That's an interesting observation you've made there. Does most of the content on your site pertain to free hosting? If so, that would be even more peculiar.
I think it might just because you dont have much content on main page? But actually it happenned to me as well that I got ads that came from domain keywords.
Thats actually not very true. Its impotant but not all the time. As long as the URL and page has relevant keywords, targetting is just fine.
In your case, you need to use section targeting which highlights the section of content about free hosting, and guide Adsense bot to crawl that section, in order to deliver more targeted ads.
Maybe ur observation is true. but adsense can use ur those content quote or phrase where u have placed adsense ads. As they say have a relevant keyword in ur file name, then they can use our domain name as a keyword too.