|I don't think it's acceptable to kiss a person on the lips as a casual greeting unless that person is your significant other, in which case the greeting is no longer casual. In fact, I think it's presumptuous to assume the receiver of a casual lip kiss has even the slightest desire for such a thing. It's fine if the giver and the receiver both agree that it's an acceptable practice beforehand. But to go in for the casual lip kiss, assuming the receiver will surely welcome it, is simply offensive.
Related: Casual kissing. #psychology