I haven't PA'd on Broadway/Off-Broadway in years, but I don't think I ever once got a job from an online posting. I went to school for stage management where I met my mentor and she hooked me up with jobs with both herself and people she knew, then I got into theatres and got to know people there and continued working.
"This table, he is over one hundred years old. If I could, I would take an old gramophone needle and run it along the surface of the wood. To hear the music of the voices. All that was said." - Doug Wright, I Am My Own Wife