The difficulty with Condition One when you're carrying a Glock is that the trigger "safety" is a lever in the middle of the trigger that requires a direct pull in order to release the trigger. If you've put your finger on the trigger as this fellow did, you've released the safety. There is no thumb safety or grip safety as with a 1911; if the trigger is pulled in this condition the gun goes off.
That's why it is so important to practice draw and presentation of the piece with the finger off the trigger. The Glock isn't the only design with this characteristic: all revolvers and many other striker-fired semi-autos are this way. "Don't touch the trigger until you want the gun to go off" is Cooper's rule on it. Most of us memorize that early on in our firearms careers.
Around the house, condition 2, at work, condition 2, while driving, mostly condition 2.
When on foot, questionable areas (when necc to be there), usually condition 1.
Being aware of surroundings at all times much more important than condition or type of carry.