When I was growing up, for a very valid reason having nothing to do with the thread, somewhere between 50 and 100 people in town, including us, had to have their telephone numbers changed.

Nobody left town over it, we just learned our new number.

Pretty sure it will be the same here, I don't really see anybody leaving United/CO because they are changing the frequent flyer number they use.

At least not enough people they really care about.