For others, public texting is a chance to cause a stir. Paul Notzold, a designer based in Brooklyn, has rigged up a system to project blank speech bubbles on to public walls. He generally sets up after sunset for better visibility and passes out leaflets explaining how to send text into the speech bubbles. “There is an element of empowerment in being able to post a message,” says Mr Notzold, who just finished a master's degree in design and technology at Parsons The New School for Design in New York. He has done a dozen or so “projections” on to buildings: in Brooklyn, along the canals in Amsterdam, in a public square in Hamburg and even on to the Millennium Museum in Beijing. “The police were around, and when they came over I thought they were going to shut it down,” says Mr Notzold. In fact, they just wanted to know the phone number to send messages to.