A common misperception in regards to a Search Engine Optimization (SEO) program is that its value is derived solely from traffic generated from Google. Traffic from smaller search engines, such as Yahoo! and Bing, holds so little value that it may as well not exist.
Just as no upstanding SEO professional would ever state that Yahoo! and Bing traffic is the primary objective of an SEO program, no upstanding SEO professional would ever state that Google traffic is the only objective of an SEO program.
In reality, traffic from all sources can bring measurable SEO value.
For instance, by setting up Analytics goal tracking, we may learn that traffic from Yahoo! or Bing may be only 10% of that which is generated by Google, but visitors convert into sale or inquiry at four times the rate. In regards to traffic from Bing, this scenario may not be as far-fetched as it first appears, as Adam Audette from SearchEngineWatch astutely points that ignoring Bing equates to ignoring a heavily e-commerce-focused demographic.
Ultimately, the answer to the question of how much you should care about traffic from Yahoo! or Bing is going to be one that is built into the individual objectives of your search marketing program, and how traffic from either source performs to these objectives. In other words, while we may not able to definitively answer this question for you, we can say that an answer of ‘not at all’ would be a definitively incorrect response.