Amazon just became the first internet giant to open up their search engine index as a platform for others to build applications on.
People have been paying attention to Yahoo (because it keeps buying into all the trendy stuff) and ignoring Amazon. But it's actually the latter who are doing all the really weird crazy stuff at the moment (like the mechanical turk)
Remember, Google's book search undermines the book publishing industry (and indirectly Amazon). This is Amazon's counter-offensive.
BTW : Battelle says "Why didn't I predict it?" but isn't this more or less what Dave Winer has been calling for for a while now? (ie. a no restrictions, open search core for people to build applications on? )
In practice, how different is this from the APIs of Google and Yahoo that things like RollYo are built on?