I was JUST wondering this myself. My cham hadn't pooped in 10 days about 6 weeks back and at the suggestion of a forum member I gave him a nice warm shower and in less than 5 mins. BOOM - I had one large cham crap.
Ever since then Samson has not pooped in his cage and it concerns me slightly. Yet I can now get him to poop by just putting him in the bathroom with the shower running so it's a little warmer and more humid in there, so I am wondering if it's more of a habit or some actual issue growing internally. I been looking and looking in my spare time and I haven't found much on chameleons poo removal parts. If I do I'll post it here and see if this is normal or actually a problem.