My thoughts too - it works in the home and at a push I can see it working for certain jobs, but it absolutely seems unworkable in public places.

But then I think again and wonder if maybe this is one of these things that seems unthinkable now but in 10-20 years, everyone everywhere will be doing it completely naturally, it's become part of the background noise of life, and nobody will care enough to really listen to what you're telling your computer to search for / do.

Yes on a silent train it might be awkward - but on the street I can honestly see it being fine, especially if attitudes and culture changes a bit as it's wont to do with new technology usage (see bluetooth headsets for a past example of this).