[color:#CC0000] When Dave says, "Sam, the next time you mention my thinning hair, I will end the conversation," Sam knows he's got ahold of something juicy. This only matters, of course, if Sam is the kind of person who -- like STBXMRSSP -- likes to have these little things in his arsenal.
If, on the other hand, Dave says, "Well, at least I save wear-and-tear on combs -- maybe I could lend them to you for your back hair," Sam knows that he's going to get as good as he gives and so there's no more incentive to pursue that course of action because Dave isn't going to respond the way Sam wants and, more importantly, Sam is exposing himself to the kind of thing he wants to put on Dave if he continues.
That sounds kind of like the cold war and the arms race...
