Yahoo "Launch" meets shopping centers
Yahoo has a service / website called "Launch." Launch will play videos & music for you, and you can tell the system if you liked the selection or not. With that information (and comparing it to other users' music taste), Launch will figure out your preferences, and ideally only play pieces that you like, including new ones you have never heard before.
It would be cool if a similar system could be used in shopping centers. In most of them, the choice of music is really horrible, and I'm pretty sure that most shoppers don't like it either. The situation could be easily solved by storing information about the individual shoppers' music taste on a customer card. Before shopping, you could "check in" to the shopping center, the system would know who's currently "in" and mix the shopping music to their taste.
Reward: Give me a special customer card that will give my music taste higher priority.