lol...
But you see what I mean? The domain name itself, while it may have an affect on the results, it doesn't appear to be a huge one. Most of the brand-name domains are usually up there because they're optimized to some degree or other.
Even if it's purely by accident. If somebody's business name is the same as their domain name - fredswidgets.com, for example - and they have "Fred's Widgets" plastered all over their site, and "Fred's Widgets Homepage" links everywhere, chances are they're going to (eventually) come up #1 on a search for "Fred's Widgets".
If your business has more of a generic name, like "Power Tools", and you register powertools.com, the name may help you a tiny little bit, but it's all useless, and overriden by other sites that have more SEO, higher PR, if you don't put any more thought into it than that.
I believe that the specific brand name domains are #1 purely by coincidence, otherwise you'd have
http://www.yoursearchquery.com coming up as the first result on ever search you do. Because of the reasons in the "Fred's Widgets" example above. If your business name (and domain name) is plastered all over every page, as it often is, you're going to eventually get pretty high.
To use your example, diamondjewelry.com, if you had "Diamond Jewelry - <product name here>" at the top of every page on your site, and a link at the bottom of your page that says...
This site is Copyright <a href="http://www.diamondjewelry.com">Diamond Jewelry</a> ©1066
That's obviously going to help.
Possibly domain name is a factor in how highly you rank (or perhaps even subdomain - is
http://forum.yoursite.com going to rate higher or lower than
http://www.yoursite.com/forum on a search for "your keyword forum" assuming all other things are equal?) but I feel it's an almost non-existent factor.
I just think too many inexperienced people see domain name as a huge factor and give it too much importance. Personally, I don't take search engines into consideration at all when picking a domain name. I pick something that's easy to remember, easy to repeat down the phone without being incorrectly spelled (hyphens missing, having a domain made up of 2 or more words where the last letter of one word is the same as the first letter of the following word, etc.), and could look neat in a fancy logo
