The dynamics of full-text searches are different than looking something up in an index, but users didn't seem to grasp this. We also saw that users didn't understand that plurals and singular words would produce different results and were surprised. Full-text searching produces a lot of irrelevant information for users. You remember an excellent article in an old issue of the Smithsonian Magazine that you think would be a fine reference. Go find it.
Indexing is a craft that takes a lot of skill.
No professional indexer with any self-respect would ever put an article about the steel industry under the topic of dinosaurs. As sites get bigger, this problem will only become more of an issue. Full-text searches will get more noisy and irrelevant as more words are introduced without any sense of what makes them important to the content. Successful searching is essentially an indexing task. To help user search more effectively, this intelligence must be designed into the site.