Companies are increasingly faced with the fact that the communication habits of their customers have changed sustainably - not only through the use of the Internet, but even more through the use of mobile services. Traditional marketing and communi- tion instruments are increasingly being supplemented or even replaced by the direct, personalized address of the customer. The most powerful tool for this kind of com- nication is the mobile phone. It provides a direct and interactive communication ch- nel to the customer. For numerous people, the mobile phone is no longer simply p- ceived as...