Facebook is introducing a new feature that will allow users to leave feedback after buying products from advertisers on its site, with the goal of cracking down on businesses that sell shoddy goods or don’t deliver them promptly. In addition to this new tool, Facebook is also warning e-commerce companies that get large numbers of complaints, to allow them to improve. If the companies do not clean up their act, says Facebook, it will constrain the number of ads they deliver and could ban them.

The Wall Street Journal reports that Facebook’s latest announcement comes only three weeks after it “published an article about online storefronts that have been using Facebook ads to flip products listed on online marketplaces such as Alibaba Group Holding’s AliExpress.”

“There are some companies that are just bad actors and we have no tolerance for that,” said Facebook product marketing director Sarah Epps. “As soon as we can detect those companies, we enforce against them, but for companies that do want to improve, we want to give them that opportunity.”

These “bad actors” operate with the hope that most shoppers won’t find AliExpress or other sites selling the same products for less money, but “shoppers have complained about misleading marketing and low-quality goods that arrived weeks later from China.” Facebook has already warned “hundreds” of such e-commerce sites.

To complain, the user clicks on his “recent ad activity to find the new tool that lets shoppers specify whether they are satisfied or dissatisfied with an advertiser’s product quality, shipping speed or customer service.” Facebook’s advice to offending companies is that they “set more realistic expectations about shipping times or provide more transparency around the return policy.”

Any business deemed to be an “obvious scammer” will be banned immediately, said Epps. “There’s a big difference between a business that’s trying to scam a person and a business that doesn’t know how to provide a great customer experience,” she said. “We’re trying to differentiate between those two types of companies.”