Jeremy Grantham, chief investment strategist of GMO, writes in his latest quarterly letter that the bursting of the two most recent equity bubbles was historically unusual in that stock prices soon recovered to their trend. The next bust, he writes, may not be as forgiving.
http://www.gmo.com/websitecontent/JGLetter_ShortestLetterEver_3Q11.pdf
Another way of looking at the situation is that these two recoveries were bear traps.
Note he called the 2008 crisis before it was fashionable, and he was never someone who was forever and a day prophesying the end is nigh.