Where's Waldo, Google Earth Style

I was a huge Where's Waldo nerd in the late 80s, so I'm loving this idea.  Canadian artist, Melanie Coles, has created a Web 2.0 version of Where's Waldo by painting an image of Waldo on a secret rooftop.  The challenge is to be able to find Waldo on Google Earth.  Google's secret and sporadic updates of its satellite images mean that it's unpredictable not only where Waldo will show up, but when.  Melanie's Where On Earth is Waldo website encourages other people to hide Waldos by providing complete how-to instructions.