it takes some really damn poor security to let someone get that close to a president with a piss-poor imitation of a security camera and no press credentials to give evidence of their identity and purpose for being there. They don't just let any random person walk straight up to politicians with a video camera or large bag in hand. It is possible in theory, but I don't think it's particularly likely.
Actually, what you say is valid in the states, but read this from not too long ago:http://www.globalpost.com/dispatch/news/regions/americas/canada/120905/montreal-quebec-pauline-marois-shooting-gunman-canada-parti-quebecois-french
Not every place has the same security measures as the USA. In fact, I think the USA might be in the top 3 for VIP safety.
EDIT: Speaking of which, Harper once came to where I work and I crossed him in the hallway while him and the VPs were going somewhere. I don't like him or his way of governing... but I'm not a lunatic. I imagine that if someone where I work wanted to hurt him, it would have been easy that day.