Senator Chuck Schumer took a break from arguing about carry-on luggage and set his sights on big banks for his latest crusade, saying they need to warn customers before ending free checking account programs. He's asking Fed Chairman Ben Bernanke to police banks like Citibank that are using checking account fees to recoup lost revenue, saying, "The new fees will be a punch in the gut of customers who rely on free checking accounts." Citibank began charging $7.50 each time a member's checking account dipped below $1,500.