Shiller (of Case-Shiller) did a bigger series of the data that goes back a centuryish. Comparing recent housing declines to the 1930s indicates the current "downturn" is worse than back then (ETA: 1932 drop, specifically; Shiller has been plugging the "worse than the 30s" story for a month or more; this a new development in backing data) in nominal dollars, then goes on to make the following startling, but inobvious point: back then, deflation softened a nominal decline (in fact, you could decline in nominal dollars in the 1930s and increase in real dollars, but never mind that now). Because our current environment is, er, the opposite of deflationary, what's the word, oh, yeah! Inflationary, the real decline is much, much worse.
Watch it kids: that's a big step.