Graffitio   is a digital graffiti app for the iPhone.  It is location based so performs better with the 3G version of the phone that has the integrated GPS system. Although billed as a graffiti app it is much more the digital equivalent of urban tagging.   Your name and a short message are posted on a geographically specific digital wall.   Walls can be of various sizes, but users can only create localized ones.  Walls the size of cities, states, and countries are a Graffitio staff only creation.    Creating a wall is fairly simple.  Once Graffitio has loaded and found nearby walls you press the + icon presently located in the lower right portion of the screen.  A map is loaded showing your present location.  If you wish to create a wall elsewhere, simply drag the map till the cross hairs are positioned above the desired locale.   The last step is to add a name then click on create. A nice simple app that allows for brief self expression.  I've seen all sorts of usernames out and about, but have yet to find Kilroy.  I would like to see the feature of designating size (or range) of the wall.  A digital version of geocaching could result with small enough ...