Some article directories have lost their PR from 5 to 4. Could this be the sign that G has started axing article directories for BLs?
When a site drops in pr it is usally because the site has lost the backlinks that it once had that mad it a pr 5 or what ever the pr was before. This why it is important to keep building links to your site, other sites go down all the time and if you a had link from that site which had good pr then you will lose as well. Sometimes losing just 3 or 4 good pr links could cause your own pr to go down. Also if the site you have links from drop in pr then so will your site, it is like a domanio effect. Just keep building links and your pr will either stay the same or go higher.
Though it can be a pain in the ass, I continue to work on backlinks every day. I motivate myself by realizing that any day where I do not add backlinks is a day where my competitors are.
Of course some article directories are too similiar to each other, causing parts of the sites to drop out of the index