The rule I learned is that the density of quilting in the border should be halfway between the most densely quilted part of your top & the least densely quilted part. So, like Martina wrote: unless the rest of your quilt is quilted with 1/2" or closer quilting, you should be fine leaving it unquilted (assuming you SID at edge of border).
Of course, the fun thing about rules is that sometimes they are best when broken.
