I have been brooding on this for a while but have been nudged into expressing it by Karen Coyle's post. I can't articulate, let alone understand, the argument as well as Karen can; but I think she strikes the nail on the head when she says that we have forgotten about classification and about the importance of subject retrieval.
When, and why, did we suddenly get ashamed of classification? Most library users don't understand how classification works; a majority of librarians don't understand how classification works; but when did we get to the point where even a majority of cataloguers don't understand how classification works? Many cataloguers think that classification is all about shelf arrangement - that classification is only the number on the spine label.
Keywords just don't do it and never will. Do a keyword search for "pain" in our catalogue and you'll find some books about pain and pain relief; a number of novels which happen to have "pain" in the title; and a book in French about bread. And yet somehow, and largely I suspect because of Google and its ilk, we have come to think that's OK.
In libraries we will never be able to out-Google Google because we don't have the enormous resources that it would take, but that's not the problem. Why do we want to follow Google instead of doing something better?
Somewhere along the road we seem to have decided that users don't understand classification and therefore we shouldn't use it. Now there is absolutely no reason for users to understand classification, any more than there is for every driver to understand the mechanics of the internal combustion engine, or for every concert-goer to be a expert music theorist. Our job as cataloguers is to provide the engine, plus just enough guidance to enable our library users to get the best out of it. And anyway, people do understand classification otherwise they would never be able to find their way around the supermarket - almost every part of our public and private world is organised in some systematic way.
Classification isn't elitist, it is an absolutely essential tool for organising knowledge. We should be proud of it, not ashamed of it.