Interesting post on how sitemaps impact the crawlers from Google and Yahoo. It's pretty incredible how fast Google is...

Quoted: Like any other person out there, I fall into habits, good and bad. Recently while working on a client’s website, I created a Sitemap and submitted it to the search engines, like I always do. I started to think if this really helps the site out and what’s the effect when I submit a Sitemap on the site.