Terravision bus is a very popular bus.  It offers the cheapest/most direct transportation between Florence's A.M. Novella train station and Pisa airport.  The bus is often overbooked, which is were the pickpockets come into play.  When waiting to board the bus, the driver calls the names of those who have reservations to board first. Instead of lining everyone up at the side of the bus so every hopeful passenger will have some space, the bus driver usually stands guard at the narrow bus door, making everyone pack into a tight semicircle, hoping to be the first on the bus in order not to miss his flight (taxi to Pisa airport is Euro 140 one way).

This is where you need to really pay attention to your travel bag, purse, or wallet.  As everyone is pressing on each other so they can hear the bus driver, you end up being pressed and pushed by increasingly desperate passengers wanting to get a seat on the bus. While you are watching the bus driver struggle with the pronunciation of names on the reservations list, it is easy for you to miss someone unzipping your bag, which is why pickpockets really like to work this location.  Consider one of  travel bags with security zippers when in a location like this.