I always put it down whether there's a person behind me or not; it's less effort for a checkout person to stick it back on the side than for a person to have to lean over and get it.
Sometimes when someone stupid-looking approaches behind I put two down with a space between them just to make sure their expired Burberry fish sticks don't touch my Tesco Finest Cheesecake.
Next-customer markers - whose responsibility? watch
View Poll Results: Who should place the 'Next Customer' marker?The shopper in front89.47%The shopper behind10.53%