Disney's wording on the limits causes a lot of this. The signs say 2 per guest. We witnessed a particularly ugly situation in October over the Mickey 50th popcorn bucket. A woman was raising HE double hockey sticks over being limited to 2. She had her two kids with her and said they should each be able to get 2 so she wanted 6, then went on to say she had 6 family members in the park and they all should get 2 as well. The CM kept insisting it was 2 per family and the woman went nuts. It was terrible. Eventually they did let her buy 6 of them, but even then she was insisting on talking to a manger to complain about how she'd been treated. We felt so bad for the poor CM's and tried to make them feel better once it was our turn in line.
You would really think Disney would figure this out by now. At the end of the day, I doubt they really care that much, as long as it all gets sold.