I think those are the biggest differences: actually asking you for permission, and (I'm assuming) no backstabbing of you constantly. My SIL has an absolutely wonderful nickname, and their neighbor loved it so much, she gave her newborn daughter the same name and nickname without asking. Granted, not the same family, but my SIL was not amused.
My husband's first cousins truly annoyed me. One stole the first name I was going to use for my firstborn if it had been a girl, then proceeded to name her son the same first AND middle name as my son! Her sister then used the same first and middle names for her daughter as my daughter! My daughter's middle name is a family name from my side of the family, and being from a different culture, has absolutely nothing to do with the cousin's daughter. I was actually shocked. Haven't these people ever heard of baby name books??? WTF?!
And no, neither asked our permission. My husband's grandmother had 2 sets of grandchildren with the exact damn names.