Redefining sound in public spaces

Recently, the excellent CBC radio program, Spark, featured a story about these "audio spotlights" from Holosonic Research Labs.
Basically, Holosonic has developed technology which has allowed them to develop speakers which can direct sound in a very narrow field, "pinpointing" that sound in a very specific direction and area. This, effectively, allows a spotlighting of sound, so the projected sound can only be heard if the listener is positioned in a very specific spot.
I thought this was a fascinating issue in regards to space, for many reasons (several of which were profiled on Spark,, the podcast for which can be found here, if anyone's interested). As can be expected, given that this is new technology, the audio spotlight was first employed as part of an advertisement. A huge billboard for A&E's Paranormal State not only towered above passers-by - it also emitted spooky sound effects, and apparently, people were initially pretty spooked. Mission accomplished. 'Where is that sound coming from?' they would wonder. Extrapolating from that, it's easy to imagine audio spotlighting for any ad. We all know how catchy jingles can be, but imagine if you heard jingles every time you walked past a bus stop advertisement. Now that is spooky.
But the audio spotlight is being marketed to private owners now. Imagine, if you will, sitting in a living room with someone who is watching TV or playing Xbox. The whole time you're trying to study, or nap, or whatever. Well, with audio spotlighting, your friend can enjoy their TV/music/videogames/whatever, and you can revel in your silence! It's kind of like headphones... but better?
The audio spotlight raises an interesting question about the ol' public/private space issue: how can we simultaneously occupy both at once? Headphones, for example, are a visible indicator of people trying to block the outside world from their perception (as I read in an article, "to avoid the horrors of mass transit"). So when you encounter someone with headphones, they may seem unapproachable. Thus, they can be used to say to the world, "leave me alone for now." With audio spotlighting, the line between private and public becomes a bit blurry...

Oh, and if anyone's curious, this is the "how'd they do that" bit, from Holosonics...