If you knew what everyone else was buying…in the grocery store?

Technology Review: Driving Impulse Shopping with a Smart Cart. by Duncan Graham-Rowe, 2006-Nov-2

Impulse buying currently accounts for about 40 percent of all supermarket purchases, says Ronaldo Menezes, an expert in swarm intelligence at the Florida Institute of Technology, in Melbourne, FL. But his research suggests that impulse buying could be significantly increased if information was fed back to shoppers about what others are buying.