For Siri: if the default system of Siri can not answer your question, it will try to search the Internet. Currently, Siri connects to the Safari browser by default, and Safari's primary search engine is Google (Can change to Yahoo or Bing). But in iOS 7, Siri's default search engine will be replaced by Bing. Siri will use Microsoft's search index to answer the questions it can not answer itself, and it will not ask "would you like me to search the Web" anymore.
Jun 12, 13