I recently stayed at POP and the day I left (02/11/09), they had new mugs on the shelves. I wish they would have been there at the beginning at my stay, I bought the same one I already have.
On the morning of the 10th, the POP manager (I assume he was the manager since he was doing it) was offering to exchange our mugs (as well as others), if we had our receipt. We did, but I liked the ones I had and I was leaving that day anyway.
I just completed my 39th trip and the only time I didn't see the sign that it was good for the length of my visit was at Dixie Landings. I still have their mug and love it. It's big, it really keeps the drinks cold and I have on occasion brought it back..just because I like to hear the old time workers at Port Orleans offer to buy it off me LOL! They actually used to have the sign with the mug ads in the elevators, and when the mugs were in yoru room, it was on the sign with the price. I used to have a picture of it from the mid 90's and posted it once on this board. But it's long gone, since I really don't care who brings the mugs back.
I will say, in spite of want the signs say, when a mug is purchased, I can't count on both hands how many times I have heard a CM say, be sure to bring it back (or words to that affect) on your next trip, and not as often I've heard someone being told they can be used at any resort. Obviously, Disney does not care, or they would have put that in the training. I have had conversations over the years with 'suits' at the resorts, and they say it's up to the individual manager of the food court. If he (or she) feels it's good for their business to encourage people to bring back a cheap mug and stay in their resort, I've been told it was their choice. I have been told in the past that the soda is not really free, but exchanged for advertising. So, if that is true, Disney is really paying for it, in lieu of payment for all the advertsiing of Coke they do.
I was entertained at the food court this last trip. I was at the toaster and the gal next to me started explaining why she was using an old mug. I started to laugh and told her I didn't care..but I had to know, was she a Disboard member, and she admitted she was. She said she had been apologizing all week for using the mug. She seemed to think people were watching her, and planning on 'reporting' her on the board. I had a nice laugh about that. Hey lady, if you are reading this, knock yourself out LOL!
I thought it was an interesting touch by the way, when we saw two different families leave their mugs on top of the garbage container. I told the second family they were forgetting their mugs, and the mom told me they didn't forget them, they were hoping someone else could use them, as they were going home and had no room or use for them. (I assume before someone starts saying..yuck, l how could they drink out of a used mug that if anyone took it, they washed it..sort of like when you use a glass in a restaurant when someone else drank out of it).
aaahhh--this is GREAT!! 
= me, seeing who the saint of the day is...
Hasn't yet. Even my 2 DD's are getting in on the act of telling me, "it's for length of stay only dad!" My DW also says, "Go ahead and post that you are bringing the mugs back with you and see the reaction you get at the Disney site". I SEE! So, we will be buying FOUR new mugs (again) this summer. I think this is our 4th set!
