It is pretty enlightening to look at properties that closed today and then look at the zestimate on them. For example

http://www.sdlookup.com/MLS-076076782-2043_Parrot_St_San_Diego_CA_92105
http://www.zillow.com/Charts.htm?chartDuration=5years&zpid=17078194

Zillow has it’s low range 12,000 too high and that is not even including the drop in the last 2 months.

Here’s another one:
http://www.zillow.com/HomeDetails.htm?zprop=17004423
http://www.sdlookup.com/MLS-086007551-3625_43rd_St_5_San_Diego_CA_9210