I have sandpaper of varying grits in my hiking/camping pack (because I can replace it and use it for other things), and the fine/finer Diafold in my BOB (because it takes ALOT of sharpening to wear it out, and its slim/light).
I can't justify carrying anything heavier. I've even resharpened my Wetterlings Carpenter with the Diafold to a shaving edge. Works great.