If you were a student in school and your teacher asked the class a question that you have no clue what the answer is. . . would you raise your hand just to tell them "I don't know, sorry"?
Then why, pray tell, do people do that online??? Why is it that when someone asks for commissioners they get "I would, but I have no money"? Or when they ask for help they get "I don't know"?
Silence = I don't know or I can't or I don't care
That being said-
STOP IT, STOP IT.
In addition to it giving annoyingly false hope, it also looks about as dumb as raising your hand, just to say you've got nothing.