Just one clarification - if indeed Disney does not allow people on the dining plan to use a credit to pay for food that someone else not in your room/on your plan is eating, that's fine, and you could say that someone trying to use the plan in that manner was not using the plan "correctly" (intentionally or, in my case, unintentionally). However, I do not think it is fair to lump that type of possible "incorrect" usage into the arena of a "scam" - to me, a scam is cheating or somehow acting dishonestly to try to get something for nothing or something for less than its value. In my situation, Disney had my money and the credits had their same value as credits whether I ate a meal or my friend actually ate the food. There is no difference in value / money to Disney if I ate at Yachtsman one night and California Grill the next, or if I use those 4 credits to pay for me and a friend at Yachtsman and skip the CA Grill (obviously just an example).
I just wanted to point this out because some people on these Boards (thankfully not many who have posted to this thread) are very quick to jump to the conclusion that anyone making a mistake with the plan (which we can all agree has some serious ambiguities in the way that it is administered), is trying to scam, cheat or pull a fast one.
To respond to a prior poster's expressed doubt about whether the manager was actually rude to us, I will reiterate that the major problem I had was his attitude and his use of an analogy that directly compared my party to people who willingly and knowingly break the law and only ocassionally get caught. Under no possible interpretation of "customer service" was his attitude, comments or behavior appropriate. If he had in a very polite and respectful way explained why he could not allow us to use the remaining dining credits, I would have expressed surprise and shared with him that that was not my understanding of the plan, but I would have let it go at that, paid out of pocket for the last meal, and probably asked for clarification at the Beach Club concierge just to make sure that the manager was not incorrect in denying me use of my credits. But the way we were treated, accused of wrongdoing, and then to have the manager imply that we had wasted his time as he went off in a huff (literally storming away from our table with a big exaggerated sigh), was an unfortunate end to what was supposed to be a nice meal and what was a really great trip overall. In the event of a discrepancy or disagreement, I believe that the manager is always obligated to resolve the situation while still treating the guests with respect and courtesy. That is not what we experienced.
This is not a moral issue for me. My conscience is absolutely clear in how I used or tried to use the dining plan. I just wanted to share my experience. The overall point is that the application of these rules and exceptions is very inconsistent from place to place so people should be prepared to only be able to use the dining plan for the exact size of the party on your room key.