iCrossing Search Strategist David Shapiro gave some good advice in a recent blog post.

To summarize, he said if Yahoo is driving a significant amount of traffic to your site, you need to determine what keywords you rank well for in Yahoo, but not in Bing, and before next year, you need to work on raising these rankings. He also said you need to determine which Yahoo terms you rank 610 for that may return Quick Tabs. With the way Bing displays search results for these queries, ranking 610 is significantly less valuable, says Shapiro. Bing returns the top five results for the primary keyword you entered, then displays the top three results for up to five related terms, providing a list of 20 possible listings for the user to select.