Facebook hack together a 42 foot wide QR Code across the roof of 1 Hacker Way, Facebook HQ.

Code resolves to facebook.com/FBQRCode and was Zuckerbergs idea to troll ariel maps. Unfortunately, depending on when mapping services take arial photos, the shadow of the roof edge encroaches too close into the bounding white space for the code to be readable by all QR code readers.