When photographing a conventional building, with vertical parallel lines, it is a convention of Western art (see Caneletto for superb paintings that show this) that the vertical lines not converge. This is why one makes the film plane/ground glass vertical/plumb. What is most annoying is a slight convergence, which looks careless. Strong convergence can be used to exaggerate height, e.g., shooting a tall building wall lying on the ground, for effect. Convergence of horizontal lines indicates perspective (strong or weak).
Originally Posted by cliveh