Check out this article about Become.com........
Become.com's Web Crawler: A Massively Scaled Java Technology Application
Interesting in an "I'm not sure I get it, but I think I get it" kind of way. Every CSE is different and if you're not happy with your performance on one of your current feeds, check these guys out.
Here's Become.com's explanation of things =)
Become.com: Getting the most from Become.com- a users guide
Enjoy =)