I understand your point. This is why I am a bit reluctant to use privex. I don't know how many witnesses use them.

What I meant was more like say the 40 was down. Are the rest that ready to take over and support this charge? I am not so sure. Also witnessing means having one node doing the job so more chance to be taken down. Actually, as a witness not in the top, it makes sense to attack and try to deactivate the other witnesses.