In the days of usenet, people found that it was nearly impossible to make bozos go away, but it was very easy to set up a bozo filter to eliminate them from one’s view of the universe.
Cory Doctorow is very excited about Feed Rinse — an RSS pre-scrub service that “Automatically filters out syndicated content that you aren’t interested in.” It’s a cool idea, but subject to “the Tivo effect”: by intentionally gravitating toward your own interests and shutting out everything else, you lose the serendipity of chance encounters.
Flipping through LPs in dusty bins is a very different experience from searching for MP3s on a P2P network. Not because the dust is missing, but because you greatly diminish the number of accidental discoveries. With Tivo, you have the same problem: Your plate is full of stuff you like, so you stop channel surfing, i.e. stop finding things by accident.
I may not be interested in reading your posts about baseball, but I prefer to skim over those rather than miss the opportunity to read your post about some freak baseball accident I never would have heard about otherwise.
These problems are parallel to the echo chamber effect, where people in online communities expose themselves only to information that reinforces their existing world view, rather than challenging it.