In case you didn’t hear, Yahoo and Bing are combining forces. Details here:
http://www.pcworld.com/article/169261/what_the_microsoftyahoobing_deal_means_for_you.html
http://searchenginewatch.com/3634578
If this goes through, Bing would have about 20% of the searches. In addition, if they continue to grow, they might get up to 25%. That would be a big deal, for the first time it might be worth it to attempt to ignore Google SEO and focus only on Bing. I for one would much rather be in spot 1 for 25% of the searches than spot 9 for 75%.