Google on its ProjectGlass Google+ page made it clear that the company wont accept Glass apps with facial recognition technology.
“we won’t add facial recognition features to our products without having strong privacy protections in place. With that in mind, we won’t be approving any facial recognition Glassware at this time.”
Apart from a huge hit as a consumer product, there are no strong privacy principles towards the usage if it.
One of the possible scenario of privacy is, Consider you’re at a restaurant or a mall, attending a visit to unknown place and your photo is captured, identified and matched against the facial database. All this is being done with out your knowledge.
So, Google not taking risk without a strong privacy protection system.
Here is the Google+ post of Project glass..
Glass and Facial Recognition
When we started the Explorer Program nearly a year ago our goal was simple: we wanted to make people active participants in shaping the future of this technology ahead of a broader consumer launch. We've been listening closely to you, and many have expressed both interest and concern around the possibilities of facial recognition in Glass. As Google has said for several years, we won’t add facial recognition features to our products without having strong privacy protections in place. With that in mind, we won’t be approving any facial recognition Glassware at this time.
We’ve learned a lot from you in just a few weeks and we’ll continue to learn more as we update the software and evolve our policies in the weeks and months ahead.