There have been covert cameras available for creeps for a long time. And these are a lot less noticeable than Glass... http://www.thinkgeek.com/product/f03a/
Yep, the 3G hardware (especially the battery) is still to big to fit such devices, which is probably why Glass also will just tether to your smartphone.
Just like I will when some stranger is pointing a mobile phone at me.
Just because it's Glass, assuming I even notice it, I won't clam up and simply think "oh well, because it's ubiquitous and cool, I'll ignore it".