The admission came from Bradley Horowitz, Google’s Vice President of Product Management for Google+, at the LeWeb conference in Paris today. Interestingly, Horowitz doesn't believe that it was a vocal minority lashing out about the changes, but the general YouTube userbase which ran into issues. Horowitz said:
Of course, it is a bit hard to believe that it wasn't a vocal minority causing the most problems, because Horowitz also said that at the launch Google didn't do such a good job with rankings and was "in a bit of an arms race around spam and abuse." More than likely, Google will continuously be in that arms race, because YouTube has one of the more active communities of trolls on the Internet. Still, the work is ongoing, and Google is pleased with the progress it has made since the launch.
source: The Next Web