A Google Webmaster Help thread has a site owner complaining that his new site that he purchased and rebuilt doesn't rank well for it's domain.
He bought stocktips.com and is upset it doesn't rank for the phrase [stock tips]. He said:
We bought this domain few months back and we're struggling to rank for our own name. We completely re-designed the website, done a good job with on-page SEO, no black-hat whatsoever, what could be wrong?
In response to that, Google's JohnMu responded saying a few things:
(1) Buying the site made it appear as if it is a new site.
(2) Buying an established site and running similar content on it in the future does help you get a jump start.
(3) Exact match domains does not equal rankings for that keyword phrase.
FWIW Just to chime in -- it looks like you have a site on a domain that has been used before, and which includes keywords that you're targeting. While that can help, you basically still have a new website. Having keywords in your domain name does not automatically result in your site ranking first for those keywords -- our algorithms do much more than just look at keywords in a domain name :-).
Forum discussion at Google Webmaster Help.