Sort of (~95% of the time, yes)...
If you entered a CC number in when you made the reservation (this would be for Hoop Dee Doo Revue, Spirit of Aloha luau, Mickey's Backyard BBQ, Cinderella's Royal Table, California Grill, or Princess Storybook Dining at Akershus), there are specific deadlines.
In the case of the first four above (HDDR - CRT), your CC will be charged the full amount of the meal/show if you don't cancel within 48 hours (I believe, double check the timing). This is true even for partial parties, if little Susie decides she wants to stay at the room (and you let her), you'll be charged for her place as well. Without a dining plan applied at the time of booking, full payment is required to make these reservations.
Akershus and CG above require CC holds. This is similar to the above except you are never charged anything during booking, and instead of being charged full price, you are only charged a nominal fee for each person (usually $10 or $15 I think). This also still holds true for partial parties though.
For any other reservation, if you don't show up, nothing happens. DDP credits are never touched without you presenting your KTTW card. (Except for the "Check out bug" where leftover credits erroneously disappear after checking out/check out time)