Seeing people around me using Siri reminds me of Nicholas Negroponte obsession about vocal command as the ideal interface to interact with machines.
In a sense he is right, since it might be the most natural kind of interaction we have. But since imitating a human interaction (with all its non verbal subtext of tone, etc.) can remain a challenge for a long time, pretending to reduce this element of difference has something weird in it. That’s why putting a finger-driven screen on the iPhone has been, to my opinion, a much bigger improvement to facilitate the use of this devices. Having a vocal-command seems a bit like a step back to me. It has always been helpful for the blind of course, and it might be fun as a new toy, but like when the voice of the GPS can be irritating, I am under the impression that there is a much bigger cognitive effort to relate to a machine acting like a human rather than operate a machine as a machine.