As a cyclist in NYC (though I'm off the bike for a few weeks, since on Sunday I got hit by an SUV while walking across the street -- in the crosswalk, walking with the light!) I've been aware of this campaign for awhile. I was really grossed out by DKNY's usurpation of this campaign for their Fashion Week stunt:
http://gothamist.com/2008/02/03/guerilla_market.php

I and my fractured tibia can vouch that motorists in this city are totally insane... you really, really can't be careful enough. On the positive side, my convalescence will finally provide me with some time to blog -- http://prefer-not.blogspot.com/2008/04/tibial-plateau-fracture.html

George Saunders's amazing short story "In Persuasion Nation" features a large green triangle as one of its main characters, to wit: "Over the next few weeks, as it practices flying during the day and meditates on these great new truths at night, it is gradually, almost imperceptibly, transformed, from a mere green plastic-cellophane corner into a beautiful glowing oblong green triangular symbol."