I can't believe that after all this time, there's still no face recognition built into Lightroom. WTF, guys. Quit slacking.
But, it turns out that the desktop version of Picasa is fantastic at face recognition. It's ability to spot faces and realize that two faces are the same person is nothing less than spooky. And it doesn't even phone home, which is totally surprising, since I thought it was official Google policy that none of their software should function at all if the Google Plus proboscis is not firmly seated and hungrily slurping your vein.
It's too bad that face recognition is the only thing that Picasa is good at. The interface is an incomprehensible mess. Interface elements bounce all over the place, none of the checkboxes remember their state from one usage to the next, and the scrollbars are... well they're not really scrollbars, they're more like some kind of hallucinatory acid-trip.
It's truly dreadful.
I guess my plan is to let it tag the faces, then figure out some safe-ish way to extract that info back into the EXIF tags, and re-import into Lightroom.
Apparently I have only 81,041 faces left to go.
There must be a better way.