I've been actively involved in the food storage industry since 1994. In 1998-1999, during the frantic Y2K storable food buying, I got reports of many local canneries closing their doors to any non-members.
Since April 2008, panic buying has started again (I guess because of fears of the direction our country is headed), but I haven't heard of any canneries closing their doors to non-members ... at least not yet.