TMI
In an age of TMI (too much information) it becomes important for every consumer to be able to put filters in place. The first phase was the simple ones - information blockers for parents, SPAM filters etc. This has X in it, so I don't want it. The second phase is relevancy - filters that sift through content to determine - based on the user's expressed or unexpressed needs - whether the content should get through, or whether it is irrelevant.
The first phase is big business for the providers, and the second phase is a big challenge. Is keyword searching about relevancy? Search engines return an enormous amount of links and many are not relevant, so really its not a great relevancy filter. The reason is because the understanding of the need is very limited in a simple keyword search. The application must have a relationship with the user over time - to understand behavior, build a profile, create some settings, ask some questions. The search engines can only do so much with a keyword search, in terms of relevancy filtering. The future of relevancy and filtering in an age of TMI is having a long-term relationship with the user so that the system can figure out really what the user wants to see and to know, and can filter out everything else. A keyword search on Google is about word matching, not relevancy - so in many ways the search engines perpetuate the TMI problem, they don't solve it.