Given the cultural connotations of kissing on the lips, I have always been skeeved out by the sight of an adult kissing a child on the lips. Logically, I know that it's probably all on the up and up, but I just tense automatically. My gut reaction is just "oh god, that's so inappropriate". To me, it's not so much the intentions of the person behind it as it is the cultural implications. We as a society (at least in the west) equate kissing on the lips with romance for the most part. It's difficult to separate them on a conscious level, much less the more instinctive ones.