Even Amazon.com Inc. has its limits.

The e-commerce giant bans shoppers from the site for infractions such as returning too many items, sometimes without telling them what they did wrong.

Amazon has cultivated an image as a customer-friendly company in part by making it easy for shoppers to send back items they don’t want. The site’s lax return policies have conditioned consumers to expect the same treatment from other retailers, adding to pressure on brick-and-mortar chains. But shoppers are finding out there are some customers Amazon has determined aren’t worth keeping.

Nir Nissim received an email in March notifying him that his account had been closed because he violated the company’s conditions of use agreement. “You cannot open a new account or use another account to place orders on our site,” Amazon wrote.

The 20-year-old, who works at an ice cream shop in Israel, said he had a $450 gift card balance that he could no longer use. “I contacted them almost every day for a week or two,” he said.