I occasionally see NOTES duplicated on my iphone, and of course in Mail too, since they Sync. I'll edt a NOTE and second one with the same title is created, rather than updating the first one. Since the NOTES are imapped from iPhone to Mail, I see the duplicates in both places.
Its a huge problem for me. I have ten gigantic lists I manage all day long - many pages long. When a dupe is accidentally created there's no easy way to compare between the two versions. Big trouble.
Mobileme accounts have been removed--everywhere I could find them.