When in the store, just wrapped around the bolt and displayed on end. That's what most places do here (Keepsake Quilting included). I always have to flip it open a bit to get a better view of the pattern and if everyone had to refasten some sort of pin or clip, it would probably damage the fabric fold over time.
It's almost instinctual to put wrapped bolts back with the loose end pointing out and that keeps the ends pretty flat when on the shelf. They may get crunched when pulled out, but they don't get 'pressed' that way in storage. Hope that makes sense...
The clipped fabrics in some stores get pretty beat up when they or their neighbors are pushed in or pulled out. There's no 'give' where the clip is. I've never seen bolts pinned, but would imagine the pulling and stress would really damage the fabric for the same reason.
At home, I store my bolt goods horizontally, stacked, no clips, just gravity. ;)