Writing about web page http://scholar.google.com/
From the FAQs:-
Google Scholar enables you to search specifically for scholarly literature, including peer-reviewed papers, theses, books, preprints, abstracts and technical reports from all broad areas of research. Use Google Scholar to find articles from a wide variety of academic publishers, professional societies, preprint repositories and universities, as well as scholarly articles available across the web.
Interesting development. Apparently, Google have done deals with publishers to let them index content which they normally wouldn't be able to get to, because it's behind a subscription barrier. If you search for "search engines", there's a result for a paper titled "ProFusion: Intelligent fusion from multiple, distributed search engines". That paper is published by the Journal Of Universal Computer Science, a subscription-based service.
Google require that participating publishers and other groups make abstracts available so that users can see more than just the existence of a paper; they can get some idea of its relevance to them. Presumably this is win-win: Google gains a new search resource, and publishers and others get to show their wares and maybe gain new subscriptions.