"When you get this far away from a recession invariably forces build up for the next recession, and indeed we are beginning to see that sign," Greenspan said via satellite link to a business conference in Hong Kong. "For example in the U.S., profit margins ... have begun to stabilize, which is an early sign we are in the later stages of a cycle."

It seems like the boats have been rising a bit too fast in recent months. I don't know what has been driving it (I really haven't been paying all that much attention), but it felt too good to be true. No one likes a market crash but I can't say yesterday's events were totally suprising. I think people just got ahead of themselves. Greenspan seems to think they may have gotten further ahead than usual.

Greenspan Warns of Likely U.S. Recession: Financial News - Yahoo!Finance