User submissions. There’s a leaderboard and people are crazy fast at submitting them. I’ve seen 30 minute videos have the sponsor sections blocked out within 10 minutes of being posted

As an example, here are the stats for my sponsor block:

You’ve saved people from 3,297 segments ( 2d 17h 7.0 minutes of their lives )

You’ve skipped 577 segments ( 10h 18.6 minutes )