pimp my rental car

Music is already piped into venues with captive audiences, like hold buttons and elevators. What prime real estate for music promotion. Imagine: leaving you on hold forever could become something customer service reps don't need to apologize for, and muzak could become a non-derogatory term.

And how about rental cars? Sure, you bring music wherever you go. But you also like finding new music and getting a flavor of the local music when you travel. So if the car you rented on your vacation in Rio de Janeiro had a surprise in the CD player that was carefully selected to suit your fancy based on everything that had been internet-stalked about you, you might listen. And given the opportunity, you might go to an upcoming concert, make a purchase, tra la la.

The point being: people on hold, in waiting rooms, on elevators, in rental cars, etc. are generally available to listen, which is a potentially exploitable situation.