You start by allowing people to rate the ratings. For instance, flag individual titles or tags 'not interested' such as on Steam. Even just a way to hide individual titles would make a system like Netflix much better to use, and bring product customers are more likely to pay for to the foreground. And then you can feed the data to the recommendation engines, which might start to learn about what demographics are using the system rather than relying on assumptions. My personal belief (as someone with zero actual experience here), is that dislikes and disinterest would be much better for generating recommendations over likes and interest. 'likes' just gives you what is popular in your familiar genres. 'dislikes' expresses your tastes.