Growing up, I was given the impression that apostates were Jehovah's Witnesses who wanted to do something prohibitted by the Bible/Watch Tower Society or who felt it was unnecessary to go out in field service. They would find scriptures to back up their beliefs and express their opinions openly.
Now, my impression is that those person called "apostates" by Jehovah's Witnesses are persons who have found information that exposes the holes in the doctrines of the Watch Tower Society as well as exposes the religion for what it really is. Because of this, the Watch Tower Society must protect the flock is fleeces by having such enlightened ones shunned. Thousands of Bethelites are depending on your contributions.