It's not the fact they are taking pictures in a restaurant at all. A few pictures is entirely reasonable.
The expectation of privacy I am speaking about, which is entirely reasonable as well, is that I can go into a restaurant with a few friends and not have a photograph of us analysed, tagged, and added to a huge database, only to be available later to everyone, especially LEO and Intelligence Communities.
That's the problem. Big Data.
You already have shadow profiles and facial/object recognition running rampant in society now. Ignorant people that have no idea the profound dangers involved in having FaceFuck exist in the first place eliminate my privacy by recording the banality of their everyday lives continuously.
The rights of others is very important. MY RIGHTS TOO. I should be able to exist in society without having a shadow profile showing me in a couple thousand different real profiles linking me to other places, activities, events, etc. in relation to other real/shadow profiles. That's a reasonable expectation of privacy. I never for one second opted in to such a dystopian society, and it's not sponsored/forced upon us in the name of security yet.
This needs to be fought tooth and nail with fanatic effort and it's a very good thing that Google Glass is getting such a cold response from restaurants and public spaces. Government is already trying to force us into a police state ostensibly to protect IP interests (as it seems to be the only real thing we produce now), we shouldn't rush towards it just because of some shiny gadgets provided by corporate america.
Having a LED as you suggest is a very good start as the problem with Google Glass is Google. If the Glasses themselves are not able to record images or analyze the environment in any way, shape, or form without a prominent visible signal to other people it goes a long way to mitigating the problem.
In such a scenario I can legitimately complain the management and walk out of the establishment the moment I see a purple light no differently than someone lighting up a cigarette. I find both equally as offensive in a public space.
What about public spaces like parks? Driving around? Walking down the street? It's very concerning that a world could exist with thousands of purple lights coming at me all the time.