Ask HN: What are the effects of like/dislike on a recommender system suggestions

Let's talk about youtube.

My [superficial] understanding of a recommender system is that it will suggest content similar to what the user liked in the past.

If that's true, is it possible that:

1. youtube will end up playing a small set of liked videos over and over again if the user deliberately likes a lot of videos that are similar on some scale. 2. youtube will keep suggesting new videos if the user keeps disliking videos, because the user never liked anything, making it hard to tell what the user wants.