In slightly puzzling news, Google appears to have pulled the Nexus 4 Android 4.2.x system images from its online repository of factory images. These files allow devices to be restored to their original state, so if something goes wrong when flashing a ROM or otherwise tinkering with your phone, there's an easy way back to stock.
Factory images for other Android 4.2 devices, such as the Nexus 10, Nexus 7, Nexus 7 3G and Galaxy Nexus remain on Google's site, so it'd appear whatever caused them to be withdrawn is specific to the Nexus 4.
Our best guess is that this might relate to the LTE situation on the Nexus 4. By changing a hidden setting, it's possible to use the N4 on LTE networks running on Band 4 (AWS), though this is not officially documented or approved by regulators. And that last part may be key -- if Google is preparing to patch this hidden LTE option out of the Nexus 4 -- as it'd be required to do to avoid falling foul of bodies like the FCC -- then clearing out earlier factory images might simply be a precaution. It's possible Google's looking to keep regulators happy by making it harder to find the earlier radio code that enabled this unlicensed LTE functionality. That's just speculation on our part, however, there may be a much more innocuous explanation.
In any case, we'll keep you posted on any further developments.
Update: Should have checked this the first time, but binaries are gone as well. They were there before, right?