I was going to mention the same thing.. what's the point of his private list if he publishes most of them anyway?
Marketing? Private list to create appearance of exclusivity.
"Republishing: PLEASE DO NOT REPRINT WITHOUT PERMISSION
Forwarding: PLEASE DO FORWARD TO SMART PEOPLE"
I think a few of the recent ones were getting posted online elsewhere, so he just started putting them on his own site - cannot remember where I read or heard that though!