Ginger Greer, a Medford, Ore., attorney who does nearly all her shopping from work without leaving her desk, has drawn a line in the sand: “I absolutely refuse to pay for shipping,” she says.

“You can find anything, anywhere at this point” that ships free, she adds. That includes a step stool for her 5-year-old daughter and a barn-door slider Ms. Greer recently bought for her closet from Amazon.com Inc.

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