Do you also ban cellphones in your office? And email? Text messaging?

If an employee wants to steal your IP, they will.

I'm not unreasonably worried about my coworkers, compared to a software-controlled camera they'd be wearing on their heads and pointing at our code, internal docs, customer information, etc.

And yes, if someone made a habit of pointing their cellphone camera at the screen all day, I would ask them to please knock it off.

I don't trust Facebook installing cameras in our workspace, or trust that they couldn't be compromised by another party who might want to watch what we're doing.

Yes. I work on a trading floor. Personal tech is a big issue in the world of private equity, investment banking, capital markets, law, medicine, proprietary research, coding, national defense, homeland security, most government roles, law enforcement, and may other professions. An employee may try to steal IP, but in the case of regulated industries, they can wind up in jail very quickly for doing so. This is no joke, and there is no room for sloppy move-fast-and-break-things jackassery.

at a company I used to work at, yes, very much so. our personal devices were checked into a locker with security before entering the secured part of the building. you were free to come back out to use it when you needed during the day. the USB ports to our workstations were covered with epoxy. the desktops didn't actually connect to the internet, so email/etc used a remote citrix connection to isolate networks. any network transfer over a set size would send notices. to be honest, it was glorious to be without the device. the shit part was everyday when leaving the office you had to have your bags searched.

You have more control, in theory, on a cellphone, and so do people around you. With the glasses you really have no way to say if they are listening or watching what you see. The phone has most of the time the sensors partially blocked by a bag or a pocket so it really can't be compared with eyewear.