For years Linkedin has been pushing people to endorse one another on Linkedin. Why? It differentiates their data set from the hordes of resumes already available in databases across the web. It also provides more color and context to profiles beyond one’s self-reported accolades. The problem is it takes work to author a synopsis on a person. And generally speaking there is a sizable response bias. Only those that have glowing things to say about someone will tend to take the time to author a blurb.

Linkedin has toiled with this for some time and finally designed a system that works like a charm…and is viral to boot.  Its called “Endorsements” and here’s how it works:

An addictive widget that increases Linkedin’s value every time you click

On the top of your profile page, Linkedin presents you with pictures of four people from your network. Next to each they ask you a no-brainer question like “Does John know about Sales?” Recognizing that John has been in Sales for the last 20 years. You feel compelled to click the button next to John in the affirmative.

Psychologists have noted that a tiny burst of serotonin is released whenever people click on links. And, seemingly exploiting this tendency in human nature, Linkedin quickly presents another person for you to click on and endorse. Its dead simple to start clicking away and feel like you’re spreading a little good karma with each person you click on.

So what’s happening in the background? Each person you “endorse” receives an email stating that you endorsed them. As it is human nature, that person will be inclined to feed their ego and want to learn more. They click on the link in the email and they in return are presented with the opportunity to endorse others.  This is were the virality takes off.

Apart from increasing engagement temporarily with Linkedin, how does this benefit them? With every endorsement, the value of their database grows. Once they hit a critical mass of endorsements for people, they will have a structured database of skills that will be invaluable for target marketing – either on the part of recruiters or advertisers.

So in summary, this one piece of UX magic, costs Linkedin nothing now that its produced, yet will continue to increase Linkedin’s value over time. Now that’s a pretty high ROI!