An Army Reserve colleague/University of Texas student mentioned to me how great it would be if you could download knowledge directly into the brain, the way Neo learns martial arts in The Matrix. I pointed out to him (thanks for the inspiration, Walter Ellison), that such an ability to learn would not necessarily be an unmitigated good. For example, what if someone downloaded the knowledge of making explosives and used it to blow people up? Or poisons, computer viruses, safecracking techniques, etc?
So let's follow this idea out to where it builds a science fiction story setting: Say the technology to download information directly into the brain exists in a future time. Yet some of knowledge that potentially could be instantly learned is deemed dangerous (justly so). So imagine a government agency is created with the authority to make sure that brain downloads only contain data suitable for the person receiving that information.
We'll call that agency "The Ministry of Knowledge."
In a world that's an extension of our own, you'd immediately have a black market in unauthorized learning, including things like child sacrifice methods all the way up to atomic weapons. Imagine the Ministry of Knowledge (MOK) at first tries to crack down on this trend through a realization that only people who know about the black market will buy from it. So new downloads of general information, which quickly become the primary means people use to learn, make no mention of any such black market--this done with the best of intentions, of course.
This measure does not prove to be enough to shut down the illegal market. Too many people know about it and communicate the information to one another, bypassing the "knowledge blockade." So soon the MOK discovers a technological fix for that--they develop the ability to alter knowledge in a human mind after it has already been input through accessing an unexpected feature of the download mechanism.
The Ministry of Knowledge eventually slips into the role of the masters of a dystopian society in which they have the ability to overwrite what anyone knows, with the result of controlling thoughts, so that only authorized ideas are ever even known about. And if someone should discover an unauthorized truth by accident, it's only a matter of time before a MOK that monitors all the brain data of every human being will wipe the information clean.
What if the process didn't work for certain brain disorders? Or only worked in part for some people? What if a tiny handful of individuals began to gradually learn the truth, while the vast majority literally could never know it...