Shit talking implies talking about nonsense or crap. People who are idle and have a lot of free time are the ones who indulge in talking crap or shit. Gossiping is also one of the forms of shit talking in which people in a group talk about someone's private and personal affairs. Shit talking is not at all healthy and one should refrain from indulging in the same. Indulging in productive conversations which give us some food for thought is what is called for.
All of us have limited time at our disposal and people who have a lot of time to waste are the ones who indulge in shit talking. Such people who indulge in shit talking carry the reputation of being a gossip monger or a rumor monger. The energy that is overspent in talking shit about people can be very productively utilized for one's growth and benefit. That is what is called a smart and judicious use of time.