Well, I think the Bing search deal would have been a lot different if Microsoft had owned Yahoo.

Yahoo management was looking to reduce the cost of running web search and advertising platforms, but ended up still having a large expense to crawl the web and basically do web search in order to enhance Bing results. And then the Microsoft ad market managed to be worse in all sorts of ways (for advertisers and publishers) compared to the existing yahoo one, plus Microsoft took a cut of the revenue. Some of that should have been better if it was one company; plus, I bet Microsoft would have sent Yahoo employees an Xbox360 or something. (I worked for Yahoo Travel from 2004-2011)