I think in a full price store, a ban would be because you return too many things, not because they think you are reselling. At the factory stores, you know a lot of people buy for resale. There is no good reason why someone would buy 5 identical items except for bridesmaid's gifts, so they are probably reselling.
Coach has such a liberal return policy that they can be hurt by a buyer that continually returns things, especially if they return them so late that they end up at the factory. I have three items right now that I am planning on returning - I hope I don't get banned.
If I got banned, I don't see how I would be eager to ever shop at Coach again.
I think they should tell those people that they aren't allowed to return anything rather than banning them.