And what, exactly, do you want FeedBurner to do? They're just using the number NetVibes gives them and I doubt NetVibes is going to give them the ability to ins

And what, exactly, do you want FeedBurner to do? They're just using the number NetVibes gives them and I doubt NetVibes is going to give them the ability to inspect user accounts to check for dupe subscriptions. So unless your solution for FeedBurner is "don't count NetVibes (or other aggregators that report inaccurately)", there's nothing for them to do.