Post-It 'don't forget your friends' by Profero

A scaled Post-It expanded to 20 times the size of a regular note will be placed at London's Broadgate Circus to draw people's attention to the dedicated website, dontforgetyourfriends.com. In addition, 48-sheet special build posters will be displayed at a number of other locations around the capital.

The outdoor ad is accompanied by an interactive Facebook game, by Profero, which asks users questions about their friends to prove how well they know them.