Wow 4 pages! I think like everything in life, people have their own opinions, some strong, some meh and alot does come down to your own parenting although I have to say I don't remember kissing my parents on the lips at all, although maybe they stopped after a while or something. Must ask mum. We are European though so cheek kissing, 2-3 times is totally normal - even for people who you have only just met.
Thinking about this more my closest gf and I lip kiss on occasion and thinking about it now, it is usually when we have been having a D&M, one of us is a bit emotional or things have been a bit hairy. We have both been through hell and back in different situations and been there for each other and are very close. We kiss on the cheek whenever we say hello or goodbye, and I know some friends don't do that, so I guess it just depends and changes for different people. She is also the only person other than family that kisses my kids on the lips and we are totally cool with that.

I think there is a BIG difference between kissing someone whether it is kids/friends on the lips as an affectionate thing and totally different to how I kiss DH on the lips.
I'm babbling now but the quick peck goodnight etc. is different to a lingering kiss with a lover.