Lorcan Dempsey points out that Google's just introduced a strategy to bring together results from many of their vertical search engines (books, images, web, video, etc.). It's called "universal search". This would have been a good thing to bring up at the presentation I did on federated searching at the Oregon Library Association conference. I was trying to make the case that search engines are really the future of federated searching, or at least worth looking at for important trends.
Unfortunately, they don't mention bringing Scholar on board universal search. I'm also wondering about the ability to integrate search appliance results with Google Search engine results. We're thinking of indexing some of our local content with an Appliance, and if we could mix results from the Appliance with Google Web and Scholar results, maybe we could put together something like federated searching with Google technology.