I have two very simple answers to the above question. First off if you are going to start a new business, and you have not registered a domain name, then I would suggest you register a domain name that has your keywords in it. I would recommend separating multiple keywords with hyphens. The reason that it is a good idea is because when people link to you in a natural manner, they may put your domain as the anchor text. If you have the keywords in your domain, then your anchor text will be guaranteed to be your keywords.

Hotels.com is a good example. They rank #1 for the keyword hotels, probably because most links pointing to them have the anchor text hotels.com or something similar. This guarantees your anchor text in any links contain the keywords you are shooting for.

Now the other thing is if you have already registered your domain, please don't go buy a new one with your keywords in it. The basic answer is that Google gives no preference to sites with the keywords in the domain. Just because you do not have the keywords in your domain, does not mean that you will not rank well for those key words. It only means that when people naturally link to you, you may not get the anchor text you want.

Case and point is my newest site http://www.article-submission-express.com. I have went out and built my links with the anchor text article submissions. At the point of writing this article, about 17 days after putting the site online, I rank on page 11 for article submissions as the keyword. Article submission, however, which is my domain name is not ranking my site anywhere on Google. I only focus on one keyword at a time, even though my guru friends state that we should try to rank for many small keywords at a time. I like to think of search engines as humans and their patents prove that is what they are mimicking. Humans can only focus on one thing at a time. I feel that the concentration of my focus to particular keywords will allow me to not only get rankings for several keywords over time, but allow me to monitor the results and make sure that efforts towards other rankings don't damage my current rankings.

So to conclude my article, if you already registered your domain, that is fantastic. Leave that domain exacly as is. Do not go out and get another domain because your domain doesn't have keywords in it. If you do this you could even get your site penalized if Google sees the same content on the two domains. They have duplicate content filters, which is why my article submission methods are so effective. Just stick to that domain and do things like article submission to a bunch of directories with your keywords in the anchor text. These are all one way links that will only help you, and you set the anchor text.