Most forms of "self-touching" fit into a body language classification referred to as Manipulators, Adaptors or Pacifiers. These are also known by their acronym - MAP. When a MAP is displayed, at best it indicates increased levels of anxiety - thus any speaker, particularly a C-level executive, an attorney, physician, or one who holds high public office should never self-touch - even in front of an audience of one. Very rarely will anyone in a typical audience have any formal nonverbal training - but particularly MAPs involving head (and especially the face) will leave the audience with a sense of unease. They almost never can tell you why, but none-the-less they feels the speakers anxiety. It's essentially transmitted to anyone watching. Barack Obama certainly knows this, and he knew it when he committed this faux pas - but he couldn't help it. Despite having a very good nonverbal skills, he has a subconscious just like everyone else - and anxiety shows itself when it pleases.