Earlier: "...Is there a particular reason why user and user_talk need to be searchable?..."

Response: I like to search user_talk pages at least because it a last bastion where over-zealous admins may not delete the content I seek. It is generally considered non-competitive, and therefore non-combative. I find it to contains a wealth of valuable, conceptualizing information. Sometimes I skip the [Go] button altogether, and I [Search] all namespaces, and I seek out the user_talk responses to my inquiry so I can gather background "noise" before reading the main page that responds to [Go]. For me, too much information is never enough! I can go to http://www.bartlby.com/ or http://www.dictionary.com/ if I want a brief synoptic overview, and I have http://www. credoreference.com/ subscription at work for pan-research. I come to Wikipedia to get what only Wikipedia offers - a community of people passionately interested in the same subject I am, and I want all the attendant "noise" that comes with it. I'm savvy enough to tune my own signal-to-noise-ratio filter, and I do not want someone else deleting whatever they think is irrelevant information because *they* think I do not want to know all that. I come to Wikipedia precisely because I DO want to know all that!