There is an app that decodes hand motion with 83% accuracy. If someone is nearby, wearing one, they can grab your security code. In San Francisco, there is a movement to ban these sorts, especially from bars, where they can secretly record other people socializing. The pejorative name for these people is "Glassholes".
http://www.telegraph.co.uk/technology/google/10924369/How-Google-Glass-can-be-used-to-steal-your-PIN-code.html
http://www.telegraph.co.uk/technology/google/10924369/How-Google-Glass-can-be-used-to-steal-your-PIN-code.html