But the concept itself is frightening to Google. It can enable searching when you are driving, taking a shower or whenever you can't use your hands to search. And a great deal of people come into that category.
And it can be a big thing in the future. And going by Apple's reputation they can leverage it to some amazing things.
Imagine a consumer Apple TV. TV's can't have keyboards but they can have a mike. Imagine finding information through speech. That can really be a killer feature, searching and finding information by just talking through a TV connected to the Internet.
Now this is just tip of the iceberg. Siri can be disruptive in almost device/scenario where a keyboard is not a practical source of input. Going by how small things are getting, Siri is the thing of the future.
Siri is shifting importance from 'search' to 'finding information' + many other things.
Google knows this damn well, 'search' and 'finding information' are really two different things. As things move on from text based search. Voice based, image based search are really going to be very important in the future.
No doubt apple is being perceived as a threat.