Are you wanting to know a little more about the security aspects of Blackberry Blend, BlackBerry has published their Security Note for version 1.0.1.
You can connect BlackBerry Blend directly to a BlackBerry 10 device using a USB connection. When you do so, data is protected using AES-256 encryption. A BlackBerry 10 device connects to BlackBerry Enterprise Service 10 for IT policy controls.
The following diagram shows BlackBerry Blend on a computer that’s outside your organization’s network (for example, on a home Wi-Fi network), and a BlackBerry 10 device on a mobile network. All communication is protected by end-to-end AES-256 encryption.
The following diagram shows BlackBerry Blend and a BlackBerry 10 device on a work Wi-Fi network. All communication over Wi-Fi networks is protected using end-to-end AES-256 encryption. BlackBerry Blend only connects to the BlackBerry Infrastructure when it needs to open a tunnel to the device for the first time. Otherwise, BlackBerry Blend can connect directly to the device.
Further topics covering the securing data in transit, data at rest, processes and advanced data flows can be found in the Security Note.
You can pick up the PDF here for some more detailed reading.