YouTube could set a views threshold to make manual reviews scale. My guess is 99% of what people watch is the top 0.1% most popular videos which makes things manageable.
Highly dangerous video seen by 5,000 people not a big deal. Highly dangerous video seen by 5,000,000 people is.
Highly dangerous video seen by 5,000 people not a big deal. Highly dangerous video seen by 5,000,000 people is.