When it comes to advertising, nothing packs more selling power than word-of-mouth endorsements. Sure, a print or TV ad can help you build brand awareness, but personal recommendations from friends, family, and colleagues prompt consumers to spend money.

Thanks to the ubiquity of social media, word of mouth is more powerful today than ever before. Not only does digital technology put the sharing of opinions at the fingertips of virtually everyone, but also 38 percent of adults say they aim to influence others when they express their preferences online.

But most of us assume that word of mouth implies some distance between consumers and the brand that’s being talked about. Word of mouth is for the people, by the people, right? It’s supposed to be organic.

Maybe not, suggests Warby Parker, an online vendor of eyewear. As part of its home try-on program, the company sends five pairs of specs to customers to give them a chance to thoroughly assess their options for new frames. Customers are encouraged (via email) to post photos to their social-media accounts of themselves wearing each potential pair. This leads to word-of-mouth advertising. And though it might still be organic growth, the company is the one planting the seed.

“Every picture that we see, we comment and give feedback on,” Tim Riley (@tmrly), Warby Parker’s director of online experience, tells Path.To. “We’re seen as the expert view, but what also ends up happening is that four or five of the customer’s friends also comment. Not only is that person who posted getting really good feedback, but then four or five more people might get introduced to the brand as well.”

As a maker of something people wear, Warby Parker is well suited to get its customers to post photos of its product. But what about companies that sell less personal items? Neil Blumenthal (@NeilBlumenthal), Warby Parker’s co-CEO, tells Build that the question misses the forest for the trees. Using social media to encourage word-of-mouth advertising isn’t merely about getting customers to use social media to post photos or content about the company; it’s about being authentic.

“You’re never going to get people to do [something] that is unnatural or unhelpful,” Blumenthal says. “Companies need to put themselves in consumers’ shoes and ask what’s really relevant to them, not just ‘Will this help me market?’”

For example, Warby Parker knew its social-media efforts would succeed because the home try-on program was already generating word of mouth offline. “People would get the home try-on sent to their office, and they would immediately ask their co-workers [how they looked],” Blumenthal says. “It exposed us to an entire [group].”

Extending the program to Facebook and Twitter simply made sense.

This article was originally published at The Build Network.