We have arrived at a time & place where we take access to information for granted. Easy, right...you type your query into the search engine and bam, you've got 100 gazillion hits on your subject. And, most of us are saavy enough to know that a preponderance of the info is total bullshit. Then it becomes a process of winnowing out the truth or at least the most accurate info you can find.
But, what if the truth wasn't even in the returns? What if it had been deliberately removed so that all you had access to was the bullshit? Being human, you would end up winnowing and you would begin to draw conclusions based on the info you had available to you, but your conclusions would be irrelevant in the overall scheme of things, because the "truth" was unavailable to you.
That is exactly the agreement the Chinese government has extracted from the search engines, like google or yahoo, that want to provide their services in China. The Chinese internet is connected to the rest of world across an electronic "gate" that has been deemed the "Great Firewall of China." It is literally a set of huge cables that convey electronic data between China and the rest of the world. Anything from outside the borders of China is highly censored at the "Great Firewall."
I experienced this for myself when I was in China in 2006. If you type "Tianenmen Square" into any search engine all of the returns are about happy tourists and history, blah, blah, blah.....or if you type "Tianenmen Square Massacre" into the search engines, it will give you a message that says "your search returned no results." Any of the search engines that operate in China do so with a version that is distinguished by a ".cn" extension. All of the search engines are whores and they agreed to it because it meant they could make money in China if they agreed to the government's censorship standards. BTW, they had to create new programs and softwares that would automatically insert the Boolean operators that would restrict the results.
Think it can't happen here?