We all know what conspiracy theories are, they are the seemingly inconceivable ideas that the government is doing something illegal, and some nut job is the only one who knows the truth and is trying to get the world to believe him. Conspiracy theories. Yes, some people do believe these theories. Some of these people even have the authority to do something about it. But they never do because they are afraid of what will happen to them.
As the Evil Overlord, you can use the power of these theories to keep your underlings in line. If word were to get out on the street that you are doing secret medical experiments on the citizens, say putting fluoride in the water, that information would have to come from someone. None of your underlings will want to admit they said something, so odds are, none of them will leak anything out. You leak information out yourself. Keep the nut jobs happy, and keep an eye on your underlings. If any of them start acting suspicious, blame them for leaking information, and then have them executed. On the other hand, you can pay close attention to what these theories are. Because if you did not leak the information, someone else did. You have a mole in your ranks, and moles need to be exterminated. Conspiracy Theories help us no matter which way you look at them.