A domain name with the exact wording as a popular search phrase can often do well because of the text in the backlinks. For example, if two sites sell 'shoes', and one site is sexyshoes.com and the other is footstuff.com, the links back to them might be something like:

<a href="footstuff.com">Foot Stuff</a> - a site selling sexy shoes.

<a href="sexyshoes.com">Sexy Shoes</a> - a site selling sexy shoes.

footstuff.com will most likely do better on a search for "foot stuff" and sexyshoes.com will do better with the search "sexy shoes". Not necessarily because of the domain name, but as a result of the way other sites link back. This is one of the reasons I prefer having the the domain name with a popular search phrase.