Running a web browser from your PC can cause all sorts of security or anonymity issues; e-g: content downloaded could be run automatically from your PC, resulting in disk encryption or other unpleasant events. It would be great if we could run most of this in a container so that we have as much of the web browser sandboxed, and limit the PC's exposure to security events.
USB devices can be dangerous to read directly from your PC. There are countless stories of PCs being infected (e-g: filesystem encrypted) because a USB device was read without first checking the USB content. But how do you check the device content without having a look at it first?!