When the IT shop at Patagonia was handed a new project to link its website to eBay's, there was no need to look for an ROI. Everyone could see there would be none. The idea was to create a branded storefront on eBay for people selling used Patagonia clothing--a rival sales channel that anyone shopping on the company's website could visit with a click.\nWhile eBay gets its normal cut, Patagonia gets no commission for any shoppers who opt to buy used clothing instead of new."EBay is a for-profit company," says Bill Boland, Patagonia's e-media creative director. "So are we--but we don't act like it sometimes. On the surface it seems counterintuitive to promote used sales, but we never thought much about it. We want to help people keep their clothes out of a landfill. People talking about it was the metric for success."The partnership brought together two development teams on two different platforms. The main challenge turned out to be a limit in eBay's public API, which caps searches at 100 sellers at one time. Patagonia wanted a much larger community.The eBay development team responded by building a custom API for Patagonia's eBay storefront. The code performs multiple, parallel API calls to avoid the limiting issue. The eBay storefront looks and feels exactly like the Patagonia website, except the photos of the merchandise for sale look user-generated, which they are. Click on an item and you're notified you are going to eBay. So far, Boland says, about 5 percent of visitors to the company's site have clicked over to the used clothing section."We thought of building our own customer-to-customer auction site," Boland says. "We started down that path, but realized it would be faster and more nimble to partner with eBay. They had the functionality and eyeballs already."The storefront is part of Patagonia's Common Threads program, which encourages customers to take a pledge to reduce excessive consumption by buying only what they need, repairing what breaks, reusing older items and recycling everything else. In the 12 weeks since the storefront launched, Patagonia got 25,000 people to sign up for Common Threads on its own site and on eBay. The company aims to collect 50,000 pledges in the first year."We [also] have a goal of getting two other companies to sell their stuff on eBay," says Patagonia Marketing Director Christina Speed. "We believe in it very deeply and think it will resonate with our core audience and bring new people to us. That's why we have a rabid fan base. It's long-term thinking. To say that it cannibalizes our sales oversimplifies how people shop. We get their business when they're ready to buy something new. When we do something wacky, it always seems to work."On Black Friday, for example, the company took out a full-page ad in the New York Times that pictured one of its best-selling items under the headline "Don't Buy This Jacket." Below that was a breakdown of the environmental cost of making the coat.The ad triggered a surge of traffic to Patagonia's website and tweets about Common Threads. Not all the buzz was positive; some accused the company of hypocrisy and clever marketing."We're drawing attention to an issue," says Speed. "We love dialogue. We're building awareness even if people are critical."Michael Ybarra is a freelance writer based in California.