Aspects of privacy
The tech is nothing new, it's the acceptance of it that worries people.
Yes you can take videos with a mobile phone or a camera placed into glasses. What Google glasses does is provide an acceptable reason to be doing so in public all the time.
Strong privacy isn't something google is good at, from trying to use MAC addresses to provide location and getting caught up in monitoring wifi to Streetview and peering over peoples fences to running and recording all searches, web history, emails and mouse pointer movements to provide advertisements.