Saw this interesting thing  on Slashdot today:
Apparently this Russian town got a crowd of people to don yellow slickers and stand in a large smiley face pattern so that Google Earth and Google Maps could capture them in their next update.
Trick is, the Google Map screen-grab appears to be a very obvious hoax by a blogger dubbed “Heiner Wolf “. According to these photos , people really did turn out to form the smiley face — I would guess as part of a radio station promotion. But this blogger transposed the people onto the Google Maps image of the area. Lame!
There are plenty of instances of messages appearing in Google Maps pics, if you want to see real ones: examples of roof ads , cool things in Google Maps , marriage proposals , and the infamous Swastika Building .