Going viral with real estate marketing is tough without seeming gimmicky or cartoonish.
However, it does work in many cases. Just ask the founders of Hotmail.I guess, you can argue that the Zillow ap went viral when they launched.
Viral Marketing tends to work best in very targeted contexts as this most recent example by the Magician Chris Angel. I love magic and how if you study it, we are taught how easily the mind can be fooled.
Check out this Viral expose.