People use the "my boyfriend/girlfriend" under the assumption that you don't know them, I think. Or they're just silly.
Anyway, I don't mind it to a point, but when they're constantly sucking face in public it's been taken a wee bit too far.
I think it's cute when a couple does that!
Meh. It doesn't bother me.
I don't particularly care about their relationship, so I'm rather annoyed when they do it.