I think that this observation is actually the key to growing a social news site without it becoming diluted, as it happened to Reddit. If you make an algorithm that simply looks at what posts you contribute to, post in and look at it should be possible to locate other users that fit into the same subset. These users submissions and comments are probably the ones that you like.

I also think there's a pretty good business model in developing a good back-end that people can use to create their own social news sites.

Maybe someone from here would be interested in helping explore it?