It is the general consensus that having the keyphrase a webpage is targeting in the URL for that page can boost your rankings in the search engines. Of course, unless the website is optimized for SEO in the first place, having the best URLs on the web won’t make that much difference. However, it is widely believed that optimal placement of the primary keyphrase for the page in the URL name can be very beneficial.
For instance, the search engines place a lot of weight on words contained in the URL as it allows the search engine algorithms to assign a theme for a page. That is to say, it just makes it easier for Google, MSN or Yahoo to understand what the page is about. This also goes for the user as well. When the casual surfer sees one of those long, multiple parameter URLs in their browser, it can be a little intimidating and may not entice them to come back and visit or bookmark the page. It is also claimed that the positioning of the keyphrase is important too. For instance, the closer the keyphrase is to the root of the domain, the more importance the search engines are likely to place on the relevance for that keyphrase.
In conclusion, while having URLs with no keyphrases and too many parameters will not necessarily make or break a website, it is the more optimal tactic to make them as search engine friendly as possible to get the most out of your SEO efforts. Of course, an already well established website that has great rankings, site structure and meta data doesn’t need to worry about such things, but the new websites should and could benefit greatly from it.