It takes work to craft the right message, good public relations professionals know. Being on point, helpful, and connective is the result of experience — you can never assume the person on the other side of the conversation with you understands or knows all that you do.
Which is why I am often quite surprised when people choose disconnection to (possibly) make a point, their point. They say familiarity breeds contempt. It must be the case in social networks — people see you often enough, and think they know you.
Or they expect to receive a meaningful exchange based upon a quick remark thrown over the fence. Why would anyone feel the need to explain something to someone who has not even taken the time to ask a specific question?
Casual does not equal causal.