But Google Inc.'s ambitious effort could herald the beginning of the commercialization of libraries, which have long been trusted as an independent resource for knowledge without the obvious trappings of marketing or goals of profit.

For the sake of wider public access, librarians and archivists are grateful and excited about Google's underwriting of the effort to scan millions of books and research materials.

Yet they also know that Google, the leading Internet search engine, relies on revenues from advertisements that are often related to the search topic.

And the agreements that Google worked out with the research institutions are non-exclusive, which means Google's rivals, such as Yahoo Inc. or Amazon.com, might try to get access to the same material Google digitizes. In other words, even if Google remains true to its word to ''do no evil,'' another search engine without the same ethics might come along.

''There is anxiety about whether the student researcher, scholar or citizen will be guided into the free public access rather than being lured into a purchasing relationship with the publisher,'' said Duane Webster, the executive director of the Association of Research Libraries.