I can see both sides of this. In fact, this is not a new idea. I and others have mentioned something similar several times.
Though Black Sheep makes a good point, I think it would hurt the Borg more by becoming more and more public and organized with our opposition. He's correct that it probably wouldn't affect those IN in a way we would like because it would reinforce their perception of "opposers" and increase their paranoia that the enemy is in their midst.
However, we could hurt the WT more overall by such public movements that would A)educate the public about the Borg, discouraging and reducing the number of converts; and B)educate the DFd, DAd, and faded ones who still believe it's "the truth" and are still living under a measure of cult mind control so that they never return to the cult.
What I would like to see is a specific date set aside each year that faders and undercover dissidents who plan to leave that year, ALL leave on that same date. I wouldn't like to encourage any of the conscious class to leave before they're ready, for the reasons Black Sheep gives in this thread, BUT IF you are going to walk out on the Borg, why not walk out on the SAME DATE as the rest of the conscious leavers each year?
I would suggest Nisan 14 as the date.