I think it's f'n off.... I think 99% of spitters, as you kind of hinted at, just do it all the time... Like out of habit because at one stage of their life they thought they were cool for doing it but never grew up...

I can probably count on both hands the amount of times i've spat in public, and they have all been because i've done a big sniff, and some seriously grose chunky sh!t has ended up in the back of my mouth... That is probably the most disgusting of all spitting that you see, but it's probably the only essential one...
Most greenie's you can swallow without any fuss... And there is just no excuse for spitting when you have excess saliva... You swallow it you tossers..

When I see young people (16 to 21) and they are spitting, i'm getting ever closer to grabbing one and pushing his face into the spit and asking him to lick it up... It's a filthy habbit and no one wants to stand in something that came out of someone elses mouth or nose...

Good one Bilbo...