I save all my scraps...you just never know when you (or someone else) needs just the "right" piece for a project. I ran across this when I needed an orange piece for a carrot nose on a snowman I was appliqueing. I found it in my scrap bag!
Also, it is nice to be able to help others on the board when they are looking for scraps. Someone just recently asked for salvage edges, so I decided to start saving those too!