Dan Frommer on the implications that Siri has to Google search:
And, more importantly, Apple is sticking itself between you and Google, by offering direct search access to sites like Wikipedia and Yelp — and many more sites and apps to come, no doubt. Siri doesn’t have to go through Google Search, and it doesn’t show you any Google ads. And that should be scary to the folks at Google, which still makes the vast majority of its profit from search advertising.
That’s a great point, though I think it all comes down to usage in the end.