Public records. it's the current "new scare" on Facebook. They know that I am a male in my late 20's and I live in an apartment that is rented, and the county assessed it's value at $185k. All info you can easily figure out with a little digging. You know way back in the day, phone books listed your name, address, and profession, right? Your property value is generally available through county records. Yatta yatta. If you happen to play on Facebook, just be sure to set your privacy settings to private and -legally- they can't sell anything.