I regularly walk around with things in my mouth.
I'm also rather clumsy, and regularly trip over.
I continue to be amazed that the two have not yet collided. Picture me whilst in the kitchen making coffee with a spoon in my mouth. I'd trip over my own feet and end up with my brain impaled on a spoon. This hasn't happened yet.
Nor have I, whilst walking around the office with a pen in my mouth (i suck, i don't chew...it's compulsive, I chew straws in movies too...) I haven't ended up with said pen stuck up my nose.
Considering that I managed to crack my sternum with my own knees, I think it's probably a good thing I don't ski with things in my mouth.