Yesterday, Google clarified their position on Dynamic vs Static URLs on their blog. At this time, they're not recommending rewriting dynamic URLs, because it's hard to create and maintain URL rewrites. Google recommends serving the original dynamic URL and let them handle the problem of detecting and avoiding problematic parameters.
As Barry Schwartz comments in his post, "Google Says, Don't Rewrite Dynamic URLs to Static URLs", this is a radical change in how SEOs handle dynamic websites. For many years, SEOs have been recommending using URL rewrites because previously Google and the other search engines had issues crawling dynamic sites. However, with recent improvements to their crawling and indexing technology, it's no longer the case. It can even cause an issue with your SEO campaign.
If you're currently using URL rewrites, should you jump on the change bandwagon? It all depends your site's specific situation. My best advice is to review your existing web analytic and search engine ranking reports. See how well your "static" URLs are penetrating the search results, and then make your decision. If you're a new site in production or just launched, you should probably stick to dynamic URLs.
