Written type usually runs across a horizontal plane, but when contrasting type by running it at different angles, can make an effective contrast. Contrast of direction has to be utilized carefully or it risks ruining the legibility of the type. If running type vertically, the whole line of type should be rotated as opposed to stacking letters for it effects legibility.
A line of type running horizontally will look shorter than a line of type of the same length running vertically. Because the shape of our eye is able to move more in the horizontal direction than in the vertical direction it makes us misjudge heights in relation to horizontal distances.