Have you ever run the diagnostics tools. You'll notice each device has it's own unique IP address. Using this, anybody can remote onto the OS on your blackberry (search through JAVA.com, they even have a handy utility for this). Using this, they then modify the settings on your device at will. I've just remoted into my Account Manager's device and composed an e-mail offering me WES 2010 tickets.
Encryption? The Blackberry encryption scheme only works when going through the RIM network. Using IP adressing, you bypass this little feature.
Better to light a candle than to curse the darkness.