I agree with the anon poster.... I guess I would be constantly going to get a tissue or cup or something. I've never carried something around with me, though that would solve the problem, but I guess I just don't like to spit in front of others -call it vanity- (at the gym, at school, at the coffee shop, etc.), and I'd just be spitting all the time.
I've never spit unless I'm giving a culture, and never had a problem that I know of. I know its gross and can't be good for me, but its habit and I don't even realize I do it anymore unless I'm really sick and coughing an excessive amount.