“At YouTube, we strive to be a place where creators of all sizes and backgrounds can find and share their voice. To ensure that YouTube promotes respectful interactions between viewers and creators, we introduced several features and policies to improve their experience. And earlier this year, we experimented with the dislike button to see whether or not changes could help better protect our creators from harassment, and reduce dislike attacks — where people work to drive up the number of dislikes on a creator’s videos.
As part of this experiment, viewers could still see and use the dislike button. But because the count was not visible to them, we found that they were less likely to target a video’s dislike button to drive up the count. In short, our experiment data showed a reduction in dislike attacking behavior.
We also heard directly from smaller creators and those just getting started that they are unfairly targeted by this behavior — and our experiment confirmed that this does occur at a higher proportion on smaller channels.
Based on what we learned, we’re making the dislike counts private across YouTube, but the dislike button is not going away. This change will start gradually rolling out today.”
Source : An update to dislikes on YouTube