This bit from an interview of Nobel lauerate Paul Samuelson really surprises me:
Very last thing. What would you say to someone starting graduate study in economics? Where do you think the big developments in modern macro are going to be, or in the micro foundations of modern macro? Where does it go from here and how does the current crisis change it?
[Samuelson's response]: Well, I'd say, and this is probably a change from what I would have said when I was younger: Have a very healthy respect for the study of economic history, because that's the raw material out of which any of your conjectures or testings will come.
And I think the recent period has illustrated that. The governor of the Bank of England seems to have forgotten or not known that there was no bank insurance in England, so when Northern Rock got a run, he was surprised. Well, he shouldn't have been. But history doesn't tell its own story. You've got to bring to it all the statistical testings that are possible. And we have a lot more information now than we used to.