I know a guy who bought a house for 590k in ’06. Throughout most of ’07, zillow was showing that his house was worth more than he paid for it.
In the last month, zillow estimate dropped from 580k to 500k, and the entire graph was revised (so it does not even say any more that the house was worth 580k recently).
To paint a broader picture: his next-door neighbor sold his house (30% more footage) for 585k; and a house very much like his across the street was just listed for 460k; and there are a couple of SFR listings in the zip code for high 300’s.