Their goal is to identify outdoor advertisements, create an altered message, and do the dirty work. Check out the picture above and below for examples. In a way, these guys have a scary black ops feel to how efficiently they get in and make a hit. For crying out loud, they even have a guidebook on “The Art & Science of Billboard Improvement: A comprehensive guide to the alteration of outdoor advertising.”
Companies would not want BLF on their bad side.
Based out of San Francisco, Billboard Liberation Front dates back to 1977 and works for free. Good luck finding these guys though, it seems like they’re more likely to find you. Seen any of these billboards around? Find more examples at their website and this gallery.