I get a lot of strange looks when I go shopping and ask salespeople not to put my purchase in a bag. Usually I carry a big enough bag that if I pick up a new top I don't need one. I do this for a couple of reasons. One, to reduce waste- plastic bags really are not as useful as they might seem and who really needs three sheets of tissue paper protecting your new J.Crew tank. Two, I'm a little lazy, so why voluntarily amass more trash that I'm just going to have to pick up off my floor two days later and take out myself. No thanks, I don't need a bag. Should I wrap it up for you? Nope, just like that is fine.
Two stores have recently come up with some creative solutions to this problem.
BlackBird in Seattle is taking donations of your old bags. They will reuse them either in their shop or at the local farmers market. (so Seattle, no?)