Clear Channel has 10,000 NFC-enabled poster sites in the UK

"Clear Channel, the outstanding out of home media partner, has launched a nationwide campaign to raise consumer awareness of their new Mobile Platform, which launched on 10,000 Adshel and roadside panels in March.
From this morning (22nd April), consumers who tap or scan their smartphone on interactive tags next to posters featuring ADi, the robot quiz master, will have a chance to win £1000 of technology vouchers in a free-to-enter competition. Anybody who answers all three questions correctly will be able to enter a prize draw and share their success with friends on social media."

Source:  Press release from Clear Channel, 22nd April 2013