"Wow! 50M hours a day of time saved seems like a lot. How could they be evil if they're getting people to spend less time on FB?"
50M hours / 1.5B DAU is about .03 hours, or about <2 minutes per person. The average person spends 1h15m on FB, this is less than a 3% drop in overall time, but likely a larger proportion of that time is spent scrolling and seeing more ads than it is fixed on a single video.
That's total time spent on social media. According to the source, Facebook's usage is 38 minutes a day. I suppose this also counts people who don't use Facebook though.
50M hours / 1.5B DAU is about .03 hours, or about <2 minutes per person. The average person spends 1h15m on FB, this is less than a 3% drop in overall time, but likely a larger proportion of that time is spent scrolling and seeing more ads than it is fixed on a single video.