There is not much wrong with over-reporting (as long as it isn't excessive) to a company like YouTube, if they need they can hire more people and they have the funds to do so. It is good to be extra cautious and report anything that might violate youtube's service. One has to be careful with over reporting to the authorities though as they aren't a business and have limited funds to work with so if you report something that isn't illegal they waste time on that instead of the bad things. That being said, don't stop reporting illegal content to either YouTube or the authorities. I don't know how well automation is so it might not actually waste many resources by over reporting because they might be able to filter it out easily.