I saw Alexandre Farto’s work on Gizmodo today.  For some of his works he uses a subtractive process, removing material to create his imagery on walls and billboards:

These works add an interesting wrinkle to the graffiti art debate.  “Normal” graffiti art done with paint or markers is removable, this is a bit more destructive.  Judging by the care and detail I’m sure permission has been granted to do these but what of copycats who might try to emulate his art in a more clandestine fashion somewhere else? Cool stuff nonetheless and worth a visit to his site:

http://alexandrefarto.com/