The application storage area that apps install to has hardware mechanisms to prevent unexpected modifications. It is one of the reasons that the Blackberry platform is so secure. But the limited size of the application storage area has been a pain to users as long as there have been Blackberries.
Originally Posted by dfb8085
On Blackberries, there are several memory areas:
Application Storage: secure persistent area for storing application code and the Blackberry operating system, along with sensitive data such as e-mail.
Device memory: persistent memory on the device, for media or anything else applications want to put there.
SD: The removable SD card, for media or anything else applications want to put there.
RAM: transient memory for use by the system and running applications.
The Device memory and the SD card are accessible over USB as removable file systems.