Now that Yahoo has begun showing BING search results, it is more important than ever to optimize for BING right?

The simple answer is no.

The actual question that should come to everyone’s mind is will this comprise my overall SEO efforts.

Search Engine Optimization is not magic; this topic is well documented. Many if not all of the SEO methods are shared across all the major search engines, with slight weighting differences amongst them. If you follow good SEO practice you will rank well on all SERPS.

There are however some interesting observations I have made. BING & Google both at first glance seem to weigh On Page SEO very similarly. However Off Page SEO seems to influence BING a little more. BING appears to give more trust to aged domains, along with target keywords anchor link positioning.

With that being said my personal opinion is that you should concentrate on good OVERALL SEO rather than worrying about a specific search engine. 

Remember content is king.