well
as a experiement I tried optimizing a site for teen nutrition, not hard competition but not without either.
I bought
www.teennutrition.net and optimized the site and gave it a few links
after 10 days it was nr. 12 at google for Teen Nutrition, so I do belive that the domain name is of some weight... I doubt I would be placed pretty good so fast without it.
I am nr 15 now.