Because granite is a natural material and is mined from the quarry in blocks usually no larger than 10 feet long most kitchens end up with a seam or two.  Seams are sometimes needed to allow for transporting the granite pieces through a home.  Not all hallways, stairways or corners will allow a large piece through.  Where the countertops will have to be carried through, the layout of the kitchen and the size of the granite slabs are the factors which will determine how many seams there will be and where they will be placed.  The number and size of the seams should be minimal.  The material used to seam two pieces of granite together is colored to match the granite as closely as possible so it is not noticeable.  The color and pattern of the granite will often determine how visible the seams are.  If the pattern is fairly consistent the seam will be less noticeable than if the granite has a lot of movement and variation as it will be harder to match the pattern exactly at the seam.