don't know if there is a single answer to this. I think in some cases it may involve an element of some posters losing their nerve that itself may in part be a reaction promoted by some of the hype that's been being pandered as homeland news the past few years. I think in other cases there may be an element of some posters deciding to exit the CZ experience and wanting to expunge their contributions in the process...... I wonder what the Wayback Machine's view on this is? ;)