Yes, I think that Yahoo and Firefox are trying to go against Google to diminish its growth and influence because I have noticed alot the past few weeks that Google is full of a lot more spam then it used to be. Of course they would want to defeat google because google is the most popular.
With as many pies as Google has its fingers in, nearly every major company in the tech sector is in some sense competing with Google for market share. In the case of Yahoo, its search engine and mail service compete with Google Search and Gmail. For Firefox, Google's Chrome browser competes with the Firefox browser. Of course, then, it's in the interests of Yahoo and Firefox to diminish Google's growth and influence.
Its been a long time since I used Yahoo, as a search engine, or Firefox. The reason is because Google has products better than them. Yahoo knows this and that's why the Yahoo directory will shutdown on December 31, 2014. To put another way you could say that Google is the monopoly of search engines.
I do not really understand this. When I open up firefox, the first thing that pops up is google.com. So if firefox is trying to go against google, then what are they going to use when you open firefox. And the same can be said for yahoo.com I can speculate.