One need only look at the global market share of the major search engines to get a feel for why that is. As of February, 2010, the breakdown looked something like this: Google, 85.74%; Yahoo, 6.09%; Bing, 3.39%; Baidu, 2.61%; Ask, 0.63%; AOL, 0.48%; MSN, 0.08%; and so on to ever smaller and smaller portions. To put that into perspective: Google has more than 14 times as much traffic as the number two slot, more than 25 times as much as the number three, and more than 1071 times as much as the number seven. So Google is, without a doubt, the uncontested master of the search engine space, and this isn’t something that seems likely to change anytime soon; hundreds of millions of dollars of development, the backing of a well-established brand, and one of the biggest online ad campaigns later, and Microsoft’s Bing is still just barely peeking above 3%.
But the relevance of Google doesn’t end simply with its search engine share. Google is also the most robust search engine in terms of it's search engine algorithms, and its discipline in investigating suspicious behavior on the part of websites. It is easier to get blacklisted from Google than any other website, and it is more difficult to get a high ranking with them than anyone else. While that might seem like it would discourage marketers from spending the time and energy on the search engine, with their market share too large to ignore it has the opposite effect: if you focus exclusively on succeeding with Google, you can be fairly confident that every other search engine will find you acceptable.
Finally, there is the question of toolbox: with such a monumental market share, and the best suite of advertising and marketing tools of any major engine, nearly everyone who dedicates themselves to search engine optimization spends the bulk of their time on Google. This creates a snowball effect: as the massive body of material already developed for Google makes it more attractive for other marketers, who spend their time analyzing Google, and in turn write even more about how to market for Google, repeating the cycle.
The community energy dedicated to understanding the Google algorithms, the number of tools built exclusively to analyze Google results, and the level of interactivity Google offers its marketers all make it the obvious choice. So, the next time you hear a marketer talking about Google as though it is the only search engine on the planet, understand that this is only because by making their sites perfect for Google, they are not only immediately targeting more than 85% of search traffic, they are also creating sites that every other search engine will likely view favorably as well.