It's not as simple as that. It's not one poor guy looking a video feed or judging ads. It would be sophisticated system that pools together many workers in ways to get quality.
So, for example, if the factory robot knocks something over, and there are 10 different people watching a few frames of video, it's pretty likely they'd spot the mistake.
Same goes for ad critiques. You wouldn't ask "is this a good ad". You'd split it up. "Is this actor better wearing a blue shirt than a red shirt" - ask 10 people.