Wrapping your head around this genre takes some doing. Especially if you are nudging 60 (years old, that is).
Mind Candy, one of LocalGlobe's investments is making waves in this space and with the help of popular mass media like CNN is helping to explain exactly (well, sort of exactly) what ARGs are about.
Mind Candy's first game originates from the alien the world of Perplex City
This piece in CNN.com should help the uninitiated.