I've never heard of anyone being charged for not showing up for an ADR at CM's. (Out of courtesy, you should call ahead and cancel if you're a no show.)
The rule of thumb is that you get charged for a no-show if you give a credit card when you make the reservation. I believe the restaurants that do this are V&A (Victoria's and Albert's), CRT (Cinderella's Royal Table), and CG (California Grill), and the dinner shows (Luau and Hoop Dee Doo).