Well I don't know what has taken place at this lake you speak of but there could be more to consider. For some reason I sence that the majority in this thread feel that one should not continue to call when birds have set their wings and are coming into the decoys but may be 50 yards or so out. I respectfully disagree.
It may be that the person or persons calling next to you were well intended but lacking in the required skill. It may be that one or more of them have been in a blind or the same lake where very skilled callers were hunting and they where only trying to do what they had seen done but didn't have it right yet.
BBVD let me share with you in the spirit of trying to be helpful or at the very least a little informative. What you may have been observing was an attempt to fan the birds so they all didn't pile into the sweet spot. This is
not a skill often observed much anymore unless you are at a large private club. When you have a dozen gunners or so in a row how do you keep it from being a gang shoot? You have callers who are able to talk to the birds and spread them so that several will have shots without interference from the blind next to them. This of course reguires that you have a flock of birds large enough to work with. My point is that they may have seen this and thought they would try it for themselves, who knows? I am not talking about a feeding chuckle but lots of calling right in the birds faces. Have you seen ducks hover over calls only 4 or 5 yards away? Some appearing to be thinking about flying into the blind to join in the good time. This is a common occurrence at some clubs. In time you will see it and hear it and you too will want to master the technique. In the mean time.......remember there are always going to be times that you wish there were fewer of those other guys who think they are having fun but are making it less then fun for the rest. Thats called public opportunity.