Con Men and Salesmen: Spot the Difference

The quote below is from an Intelligent Life piece about con men via Marginal Revolution. Oddly, I've often said the same about skilled salespeople:

It requires avid study of psychology and body language. It's an amazing paradox--a con man has incredible emotional insight, but without the burden of compassion. He must take an intense interest in other people, complete strangers, and work to understand them, yet remain detached and uninvested. That the plan is to cheat these people and ultimately confirm many of their fears cannot be of concern.