Chicagocrime.org a web site with all reported crimes in Chicago, browsable by time, type of crime, type of location, and lets that be viewed through Google Maps.

Now you combine that with HousingMaps (a clear inspiration for Chicagocrime, I guess), search for housing at Chicago, and what do you get? The semantic web, a map plotting housing availabiliy and price in relation to crime rates in a given city.

In this case, the area with more terrible crimes has almost no Craigslist listings shown at HousingMaps...

Compare images for Homicides and the cheapest as well as the most expensives offerings: