I hypothesize you can think of the market like a big mesh net. If the price of a house drops (Eg Bothell Countdown), it pulls down prices nearby, just like putting a bowling ball on a mattress compresses parts of mattress around the ball. If prices drop 20% in Bothell, it suggests they might need to drop at least 15% in Kirkland.
So, imagine a huge net covering King County. Imagine a pair of fingers grabbing at the net from above pulling prices up (these are usually job epicenters, like MSFT campus in Redmond). Now, imagine a thousand smaller sets of fingers pulling down. These are all the houses sitting on the market, going through priced drops. Just as the fingers pulling up have a localized effect, each price drop has a localized effect to pull prices down.
Today, we are seeing marketplace innovation empowering the downward pressures, just like they before to empower those upward pressures. The problem for sellers, is that even a powerhouse like MSFT can only lift so much dead weight. There are just too many houses pulling the market down a little piece at a time.