Even without a lesson in torts law, I know that tampering with the property of others is a huge no-no. Do unto others and all that.
However, my reaction to the kid who stuck a piece of gum on a million-dollar-plus painting was a subversive "Attaboy!" Is there anything more pretentious than the dull, cold world of abstract art? Is there anything more boring, for a 12-year-old lad, than going on a school field trip to a museum of modern art?
Since "The Bay" isn't exactly a Raphael, the gum probably blended in nicely.