In the last 6months Google Adwords have made some interesting changes to how it displays the creatives for creatives in the tops positions. What happens is that the site base URL is diplayed next to your headline creative.
This now opens up the viability of using ketword rich URLS for paid search to get the jump on the competition. We all know that search phrases in the query are highlighted boldin the search results, by using keyword rich base URLs for PPC we can now highligh more of the top row of the searchadvert headline and make a better visual impact on the SERP.
I will add on small caveat though, I have seen that some creatives do the hold true to the new methd that Google is using for displaying paid creative.
If you measure the potential cost impact of purchasing a keyword rich URL and then pointing that to a product specific in-site micro-section of content that supports the URL then I feel that the spend impact and the relative increase in CTR could potentially pay for itself in a single day of traffic and also the side bar issue of better SEO'able content specific URLs thn this could be a win win situation. In other words - what can you lose.