Yahoo and Bing
 

Yahoo! and Bing signed a deal which would make them partners rather than rivals in the search field. Together they formed Search Alliance making Bing, Microsoft's search engine the one that would be behind Yahoo! The merging of search results began in North America in August 2010 but did not occur in Europe until a year later. The merge of the two search engines was launched in Europe in August 2011, but seems to be irrelevant in terms of numbers of users who actually don't use Google in Europe. What�s your idea on this?

well it looks like they are combining to give a hard competition to search king Google.

Thats really a bad new for google now may be they will be the top search engine.

Both are equally important. Without good on page seo, you will not be able to do good off page seo. If you have weakness in one technique then other technique will be valueless.