Google has slightly changed online help manual for the Nexus 4, removing references to USB support for mice and keyboards. Previously it said that this is possible using an adapter, but now the page just says:
You can connect a keyboard, mouse, or even a joystick or other input device to your phone via Bluetooth and use it just as you would with a PC. USB is not supported for connecting such devices.
This isn’t a drawback in my eyes. However, I’m not sure whether this also includes USB OTG (On The Go) that allows users to connect their smartphones to an external storage device like a flash or hard drive. Hopefully that’s not the case, as it would make an 8GB Nexus 4 owners stuck to what they got, prompting them to constantly upload photos and videos to the cloud (or move them to a computer). That would be a shame, don’t you agree?