I think one of the biggest concerns with chameleons is females becoming egg-bound. My cousin had a veiled chameleon that recently died due to being egg-bound.

The following is from http://www.veiled-chameleon.com/:

First and foremost, I cannot stress this enough, if you have a female veiled, she is GOING to lay eggs or die, regardless of whether she's around a male or not. You MUST, absolutely, have a 6 inch deep pan of sand (preferably playsand, not something used for building materials) available for her to lay eggs in or she WILL become eggbound and die.
That's worded a little dramatically... but you get the idea.

Like the others have said, do tons and tons and tons of research, be a stickler for the set-up, and make sure you provide the right environment if you get a female.

Good luck!