I remember a post from JMG (The ArchDruid Report) where he was covering Apocalyptic religions in history,and when he got to JW's he said that they were in a class all their own. Most groups that promised but couldn't deliver, faded away into obscurity. He was amazed how the JW's had pulled it off multiple times.
I will look for a link to the series he ran. I think it was snippets from a book he wrote that he included at the end of his regular posts a couple of years ago.
Edit: looks like he was taking excerpts from this:
One of his latest books is Apocalypse NOT: Everything You Know About 2012, Nostradamus and the Rapture is Wrong.