Kind of a personal story, but my fiancé is from Beijing. She found out about Tiananmen square about a year ago. She only knew that she shouldn't ask about the Tiananmen incident growing up and that it was a bad thing that happened. She has been in the states for several years now and when she found out what really happened with our even blurry images and stories we have now it really changed her perspective on things…
A couple of years ago, I spent some time in South Africa. At one point I asked a local friend what they thought about the song "Sun City"[0], which was an anti-Apartheid song from 1985. My friend never heard of the song and was shocked since so many big artists performed on the track. They proceeded to ask their friends on Facebook, many of which were in theirs 30s/40s, if they heard the song, and the far majority of them also never heard of the song. The government was very effective in blocking access to the song via all the normal channels for the time.