I don't see this being abused... :)

I visited a modern Aquarium last year and they were doing some neet stuff with sound. Above many of the displays was a parabolic reflector that directed a beam of sound ONLY to the area immediately in front of the display. If you moved 1' away you don't hear anything, but if you are within the zone you could hear the presentation clearly. One room had 5 or so displays all talking at the same time, but instead of a cacophony of sound, all you could hear was the people milling around until you stepped into one of these zones.

Practical application #1: Cubicles. Luckily I have an office with a door, but as I walk down the rows of cubes I hear 10 different songs playing from 10 different cubes, all of which are annoying other workers who don't want to hear any of it. Earphones aren't always practical (or comfortable).