Face recognition is not [and was never] meant to be used as a personal security tool. It is a crowd control/ mass security tool.
It is basically used to pick out known threats [whose pictures are with the security agency] from the crowd quickly and more efficiently than a human guard.
It works by identifying and looking for "nodal points" like:
Distance between eyes
Width of nose
Depth of eye sockets
Cheekbones
Jaw line
Chin
All these can be easily and acurately replicated in a photograph.
Fooling personal face recognition is no big deal. But im sure a person holding a photo over his face, moving through the crowd would get noticed! [and arrested !?]
In fact face recognition is used in most US airports and was recently used at the superbowl to monitor crowds.
But dont even think of protecting you comp/assests with it. Even the guys who make the software, Visionics say so. [The software is called faceit!]
It can be a cool tool to tag your photos though.