Re: don't get it
People want to pay to put a HUD on their face. A camera adds functionality for things like Augmented Reality, or just replacing a separate bullet cam/GoPro.
As for invading people's privacy, I don't get this. Okay, sure you could walk around with it recording, but you'll fill the storage pretty quick. This idea of streaming it back to Google to run facial recognition just doesn't hold water - who has data plans that would permit that (and not burn through your allowance in about an hour)? Even if Google applied some magical compression the constant transmission would kill the battery. Most mobiles can barely last a day even just making a few calls and some light browsing.
Streaming 720p for 10 hours? Show me the AA-sized cold fusion reactor.
Yes, you could manually just record everything you see - you being creepy rather than google, but that's no different to leaving your phone poking out your top pocket recording video, wearing a button cam or covertly recording sound from a pocket. You can't blame google if users do that - just as you can't blame Apple or RIM if users of their phones quietly leave the voice recorder running to capture your conversation without telling you.
Yes, they could run facial recognition on a video stream. It's technically feasible, but it's not going to be underlying the system. And if they tried to sneak it in under the radar (sometime in the future when we all have unlimited 6G connectivity) you can bet a clean version of android would spring up to side-load just as SRWare Iron popped up as an alternative to Chrome.
More to the point, why would they try and sneak in a system to harvest video and run facial recognition? That's expensive both in bandwidth and compute. Glass doesn't even have GPS unless you've paired it with a phone that does, so in it's unpaired state it doesn't actually know where you or it are.
It'd be far easier to build a surreptitious GPS tracker into the Android kernel, and quietly listen in to your phone's microphone for voice recognition - you know, the one in your pocket that could be pinging your exact location along with an audio feed from an open mic without even the owner knowing, never mind the people around them.
Lat/Long are just a few digits - far smaller and easier to process than running computer vision to match a person against a location, and quietly streaming audio back would be far more effective for conversation analysis than disjointed snippets of conversations as someone wearing a Glass unit walks past.
I get the privacy concerns, but if Google wanted to track and spy on everybody, there are far more effective ways than trying to harvest data from a handful of headsets (compared to the number of Android handsets they have in circulation).