If there's a topic that you really care about, it helps to have trusted sources who also care about it in the same way that you do. Even though that means they might share your biases, it also means that they will notice and report information that matters to your shared interests.

For example, if you have a religious or ethical injunction against eating particular foods, and you want to know whether some food product meets your requirements, you probably need information from other people who share your specific rules.

If you're kosher or vegan or locavore, you don't need some random dude's opinion about whether a particular food is kosher or vegan or locavore; some random dude might well be a troll trying to trick you into eating foreign cheeseburgers for the lulz. You need information from someone who cares about the same thing you do.

If you care about your town government's decisions — like whether there should be a new bike lane put in on one particular road — you're probably not going to get good information from a source that isn't local. And you might additionally care about whether that source is a frothing anti-cyclist maniac or a wacko "fuck cars" ideologue or an "everything the government does is thereby wrong" libertarian or something.