Even using a cell phone in the bank's lobby may result in the person being asked to leave the premises.

"We ban cell phone use in the lobby because you don't know what people are doing," Ralph Oster, a senior vice president, told the Chicago Tribune. Cell phone cameras are also a worry.

Oster said there have been holdups in which bandits were on the phone with lookouts outside while committing bank robberies.

"You're trying to stop that communication," he says.

Banks in Mexico City banned call phones in May and Citizens Financial Bank of Munster, Ind., asks customers to turn off their cell phones.

West Suburban Bank, based in Lombard, Ill., barred customers wearing hats in January but has not moved to silence cell phones.