The communication means of people that probably oterhwise wouldn't have much to say to each other.
Seen at "Harrods" in London. Great Britain. September 2010.
Canon Powershot G10, 6.1 - 30.5 mm f 2.8 - 4.5 @ 18.1 mm, ISO 200, f 4, 1/5 s. Exposure compensation -0,33 EV.