Not sure if this qualifies as street art, but Abu Dhabi Sheikh Hamad bin Hamdan Al Nahyan gets points on scale alone for this tag—it's 2 miles across, and a half mile high—made up of canals dug on a sandy island in the Persian Gulf.
The Sheikh is no stranger to extravagence. According to Forbes, "He is said to own more than 200 cars, including seven Mercedes 500 SELs painted in the colors of the rainbow." Hence his nickname, “The Rainbow Sheikh”.
Baller or epic billionaire fail? What do you think?