The map is called whydontweownthis.com (Leaflet is used, not sure what else) and is from a company called Loveland Technologies.
The company and supporters argue pulling the already public data from a variety of website into a single map "will help community leaders and residents learn more about neighborhoods."
Not everyone likes the data that public.
... housing advocate Ted Phillips said he worries the detailed ownership information will mostly help those with ill intent, like speculators and scam artists, and not poor people without computer access. He said he already gets frantic phone calls from owners facing tax foreclosure who have been contacted by people who want to buy their homes.