It's too late! Have you seen another search engine make a dent in Google's market share? How about another OS challenging Windows on a PC? Another social network? It is rather obvious that: if the main purpose of a business is to grow revenue/market share, if successful, it will eventually grow to close to 100% market share. This situation, commonly known as a monopoly, cannot be reversed by free market competition a…
Google has been doing a good job in maintaining the technical superiority of their search engine and haven't provided a serious incentive for people to switch, even though they came close with their whole Google+ clusterfuck.
That said, Bing and DuckDuckGo did make a dent in Google's market share, it's not much, but it's significant enough that they'll still exist for some time. The problem of Bing and DuckDuckGo is that they are optimized for the US market, not for the international one. As I kept telling people, the search results of Bing and DuckDuckGo in Europe are horrible.
But Google can lose against local search engines. Baidu is the primary search engine in China, not Google. Yandex is the primary search engine in Russia, not Google.
> How about another OS challenging Windows on a PC?
OS X hasn't won a majority, but it won the market that mattered - that of professionals and software developers. At this point, for most users, Windows is nothing more than a shell for your browser, or for games distributed by Steam or through PirateBay. If it weren't for Microsoft Office & Exchange keeping it alive in enterprises, it would have been long gone.
Even so, both OS X and Windows are going to be cannibalized by Android and iOS. It's going to be a sad day for those of us that were born in an era when computing wasn't locked down in walled gardens, but make no mistake as it happens. Chrome OS has been quite successful and Google is merging it with Android. Microsoft themselves have seen the writing on the wall, hence their desperate attempts to inflate the Windows 10 numbers and make it seem a success.
> This situation, commonly known as a monopoly, cannot be reversed by free market competition
You're wrong, free market competition works, but not in the way you think it does. You can't beat big companies at their own game, since they have huge resources that you don't, but you can invent technologies that make old monopolies irrelevant. Read the "Innovator's dilemma", it happens all the time.