The electronics maker tags urban buildings with black spray-painted images of child consumers absorbed in the handheld. Advertising firms call it genius, but the word on the street is less flattering. Seeking to market its handheld game device to hip city dwellers, Sony has hired graffiti artists in major urban areas to spray-paint buildings with simple, totemic images of kids playing with the gadget. But the guerrilla marketing gambit appears to be drawing scorn from some of the street-savvy hipsters it’s striving to win over.