I just ran into a search on Google that you may find interesting. Do a search on the term ppc spy. Even with quotes it has over 50,000 competing pages. It has no content or even meta tags, has been registered for about 2 years, but has no backlinks. Yet it's ranked #2. Even if they bought an expired domain you'd figure they would lose PR and backlinks and the page would drop. It would be interesting to see if it's still there in a couple of weeks. Oh, I forgot, maybe the unique content thing? http://www.google.com/search?hl=en&q=ppc+spy&btnG=Google+Search&aq=f&oq=
My guess is they just plumb forgot about it, if not I'd at least get something up to try and keep that ranking. Once I forgot about a domain I registered while it propagated and by the time I noticed it was on page #2 (may have been higher). But the point is keywords in the domain do make a big difference.
yup, it does make a big difference, actually, I do used my main keyword as may blog URL domain... ;-)
Keywords in the domain can give you a huge head start. The other school of thought is branding - using a domain that is cool, memorable, and unrelated to the topic. But that's a very long-term strategy, and in this day and age the competition is so unbelieveably fierce that you need all the help you can get Branding is the way to go if the industry is not too competitive, you are patient, and plan to make the website super-valuable and sell it some day. I've had good sucess with both approaches. Keyword domains get results quickly; branded domains are slower but more classy.
Having keyowrd in url is great and can definitely put you ahead of the rest. I just bought a spanish domain with the keyword in the URL for that niche and get about 50 uniques daily without any backlinks.