Are people forgetting WM had a voice search and assistant long before Andriod and iPhone even existed? It actually offered more than Google, but not a slick as Siri.
Google have also stated, despie it being another stolen idea, they are really worried about Siri.
Just a little. Probably also for the fact Siri rarely uses Google when it searhes, which means Apple might be getting ready to sever ties with Google, a pretty hefty loss for Google (Also iPhone Google users like myself I guess.)