Try to view what YouTube listed until recently as its most discussed video of all time and you get this page:
The woman appearing on the poster frame for the number one spot, "Truth about Islam from an ex-muslim", appears to be Wafa Sultan, a Syrian-born psychiatrist who now lives in the U.S. She has spoken out against Islam, warning that "The clash we are witnessing around the world is [...] a clash between a mentality that belongs to the Middle Ages and another that belongs to the 21st century [...] It is a clash between freedom and oppression."; words that sound remarkably like the warnings one can find in the writings of another fugitive from Islam, Ayaan Hirsi Ali.
Of course, there has been no reply. The page listing the "most discussed videos of all time" is different now: the video in question was purged from the list about two days after I sent my email. This means that YouTube's list is a deliberate falsehood; the videos shown there are not in fact the most discussed, but rather the most discussed videos that have not been removed yet in response to Muslim demands.
And there can be little real doubt about what happened here. Muslim censorship of YouTube is not new. YouTube is now owned by Google, which has been famously cooperative (link dead now) with the Chinese government in censoring its search results returned to Chinese citizens. Perhaps those experiences have taught them that they can bow to demands for political censorship without risking their market share nor the embrace of the techno-literati.