I was, carrying the back up mags in my pants pocket. Had an issue with a CZ75 magazine not feeding (on the back porch, not when I needed it) and found it pretty nasty with dirt/dust. I cleaned/lubed the magazine/spring and it worked great, again.
I just bought a couple IWB single mag pouches and am currentlly trying them. Not nearly as comfortable as the mag in a pocket, but the mags are staying clean inside.
My only question on these would be finding some way to attach them inside the pocket, so I could grab just the magazine to pull out and insert in the pistol, leaving the mag. protector in the pocket.