The Google Operating System blog offers some thoughts on Google's evolving approach to Universal Search (where they group results together from various Google indexes--Web, Books, Images, News, etc.). Even though Google has direct control over its various search 'silos', they are not trying to mix results together in Universal Search. Whether this is due to technical limitations, usability, or a combination of both, we can't be sure.
Trying to intermix and collectively rank results from a wide variety of search systems never seemed like a good approach to me, but that's just what many libraries have been attempting to do with federated searching. If Google can have its silos, why can't we have ours?
Maybe the Google approach reflects the utility of searching for the same type of media: news stories, web sites, images, products, etc. within the same search. Following on this logic, should we stick with the idea of keeping article searches separate from books in library search offerings?
Our library is thinking through these questions as we attempt to package our major search options into a search widget for our website.