Boogybonbon.com has revealed how you can potentially de-list your competitor’s site from Microsoft’s search engine. In short, most sites return a 200 status header for when you go to a page like domain.com/index.html?test=test or domain.com/index.html?test=test1234, etc. You can play on that by convincing Microsoft that a particular site has hundreds or thousands of duplicate pages, and at some point, Microsoft may penalize the site with a duplicate content penalty, where they de-list your site and home page. That is the short story, if you want the long write up visit Boogybonbon.com.
Postscript: Other coverage at Threadwatch and Search Engine Watch Forums.