It doesn't bother me when others do it. And I don't mind doing it myself. I had a boyfriend once who didn't want to do anything in public (even kiss) because other people would see it and then go home and fantasize about us. I don't know why he thought that or why it would bother him... wouldn't bother me.
Pecking, hugging, etc=not bad. Sticking each others' tongues down each others' throat=UGH! OR... Solution to that would be... If they don't want to see it, tell them not to look! HAHA! That's what I would do!