Why is Siri important?

As people get more used to the new iPhone 4S it seems that Siri, as I predicted back in early October in this blog, is becoming the stand out feature. People are reportedly buying the new iPhone 4S just because of Siri and some commentators are hailing a new revolution in how we interact with computers. By far the best article I've read about Siri is called Why is Siri important? by Brian Roemmele in Quora.com. In it he traces the origin of Siri back 40 years to DARPA funded work at SRI and describes how SIRI works in a better way than any other (non-technical) writer I've come across. Of particular relevance to people who are developing iOS apps is this excerpt:
    "Once one really understands how people will use Siri it is not too hard to see that quite a number of very popular apps and sadly some business plans may become redundant or perhaps less useful. The new model may not be apps as much as structured Cloud APIs to deliver data to Siri.  Over time it is perhaps easy to see the ecosystem that will develop around Siri and the APIs that are allowed to connect.  I am not at all predicting the end of apps as we know it in any way or form.  However I am predicting that we will see a Darwinian adaption to the new ecosystem Siri will create.  It will be of very high importance to see this trend developing and adjust business models accordingly. Perhaps the opportunities that will be available for Siri backend cloud APIs may be as large as the opportunity the iTunes app store has created."