One of my dearest friends calls me "boo", and when he calls me that, I almost don't hate it because it has a sweetness to the sound when he says it, BUT I hear it used in TV shows, movies, overused in social sites. I know it's really an old term of affection and it belongs to the culture from which it evolved, and should not be used between acquaintances or ordinary friends, because it sort of implies a type of intimacy that goes a little beyond nominal familiarity between to two people.
Pet names are really annoying in the first place, and I live with "honey" and "sweetheart" when used appropriately, but "boo", hmmm . . .
It just sounds pretentious and meaningless coming out of the mouths of those who use it with everyone they know, and is one of the more obvious attempts at being trendy and reveals the disingenuous poser inside, lol, i dunno. It just irks me.