A touchy subject with strong feelings on both sides. I come down on the side against leaving Disney Dollars for tips.
Some people will say better to leave DDs than nothing. Of course! But it would be the rare circumstance to find one's self with ONLY DDs and no cash and no credit card, etc. For those on the Dining Plan, tip is already included.
A CM who receives DDs has 2 choices: trade it in for cash, or spend it on Disney property. To cash it in, they have to go out of their way and spend more time retrieving the money they already worked to earn than if they received cash. And having to spend it on Disney property is no bargain. I mean, we all know Disney's prices for merchandise are inflated, so by making the CM spend their tip money on property, it's actually like giving them less buying power. [I live in a resort area, and it's not even a resort owned by a single company like Disney, but the prices around here generally are so inflated, I go to the mainland rather than shop on my island if I need "touristy" things like sunscreen, film/disposable camera, etc.]
I love using Disney Dollars. Last time I went, I accumulated them in the months leading up to our vacation, and we had something like $300 in DDs that we spent during our week there. I think it's fun, it's cute to have them and spend them. But to someone who works at WDW, DDs are not cute, they're not fun, they're an inconvenience. Again, I know that someone getting a DD tip is better off than getting no tip at all, but c'mon, the reality is that we as customers are almost never in the position to decide ONLY between tipping with DDs or stiffing the CM. And after all, we're leaving a tip to compensate that person for a service they provided us, we're not tipping them in order to have a good time doing it.
I'm sure it's tough to get the feel and meaning I'm trying to convey here. I'm not flaming anyone, I'm not annoyed or incensed, I'm not making this into a monster problem, I'm not blowing anything out of proportion, I'm just explaining my thoughts in detail.