ABSTRACT
It is hard to imagine a world without the mobile phone: The personal convenience it affords has revolutionized the way people communicate. Mobile phone use is almost ubiquitous in developed countries and is becoming rapidly integrated in developing countries. In 2010, there were an estimated five billion mobile phone subscriptions worldwide, and these subscriptions were increasing at a rate of two million every day (International Telecommunication Union, 2010a). Although the number of subscriptions does not necessarily reflect the number of individuals using mobile phones (one person can have multiple subscriptions, and one subscription may serve multiple users), we are fast approaching a world with one mobile phone subscription per person.
