On its surface, the sole function of Yo is for a user to send the word "Yo" to any other friend using the app.
And yet Yo recently received $1.5 million in funding, putting its valuation at between $5 million and $10 million. Its co-founders, Or Arbel and Moshe Hogeg, say that they were offered far more. Yo has been downloaded two million times, and its 50,000 or so active users have sent more than four million Yos. If Yo is a novelty app, it's the most successful one in history.
Here's the key to Yo's successful seed round of funding, and it isn't that Silicon Valley is in some kind of late 1990s-style bubble: Yo isn't what it has been widely misconstrued to be. It isn't a messaging app, and it definitely isn't a social network—on this point, Mr. Arbel is emphatic. It isn't even really a place to "Yo" your friends, though early adopters say they use it to let others know they are thinking of them.
Yo, says Mr. Arbel, is a communications protocol. Other communications protocols you may have heard of are text messages, email and Twitter.
At the risk of convincing the tech cognoscenti that I've lost my mind, I'm here to tell you that Yo—or a Yo-like service—is the next Twitter. It might even be bigger.
Here's why Yo is important: Yo provides any person, business or Web service direct access to the notifications tray of your smartphone. Every time we glance at our phones, these are the alerts we see on our lock screens, and they also interrupt us whenever we're doing anything else on our phones. Alerts, or so-called push notifications, are the most valuable property in the entire media universe, considering how often the average smartphone owner glances at his or her phone.
But wait, you say, a "Yo" is just that—a single, meaningless blip sent from some other random Yo user, carrying no information other than its source and the time of day that it was sent. That's true right now, but the next version of Yo, which will be rolling out in the coming weeks, includes a number of improvements that will turn Yo into a legitimate messaging platform—more like a Twitter or a WhatsApp, but simpler in ways that distinguish Yo and could lead to new kinds of utility.
Yo's next iteration will let users send a link along with their "Yo." And a forthcoming service that lets any person connect an RSS feed to Yo means every blogger, website and media outlet on earth will be able to send push notifications to their followers, including links, whether or not they have downloaded a corresponding app. I wouldn't be surprised if "subscribe via Yo" became a button on articles alongside Facebook and Twitter share buttons.
Mr. Arbel says other improvements are coming to the Yo App, including profile pictures for Yo users, and the option to display to followers a person's or organization's real name instead of their user name.
Yo is even getting an app store, of sorts, where services that integrate with Yo will be featured. Presently, Yo-based services include one that will let you know whether there is a bike available at a designated Citibike bicycle-sharing station in Manhattan. Another developer figured out how to make Yo part of a secure system of login known as two-factor or device-based authentication, which I've advocated before: Users can "Yo" at their laptop from their phones in order to unlock it.
Or imagine getting a Yo on your phone when your table at a restaurant is available, or you're next at the doctor's office. Israelis can already get a Yo whenever rockets are incoming.
Sure, you could get these notifications via a text message, but many people don't want to hand out their phone numbers to just anyone. Also, in most of the world carriers charge per text—hence the popularity of free messaging apps such as WhatsApp.
One challenge Yo faces is that, because the original app was so simple and easy to code, it has already been cloned multiple times, and parodies of it litter Apple's app store. (Yo is also available on Android, Windows Phone and even Amazon's Fire Phone.)
The question for Yo's founders is whether Yo can build enough momentum to capitalize on the fact that they were the first to be willing to create an app so simple, so "stupid," that no one else had thought of it previously.
Thanks to widespread disbelief that an app this basic could get venture capital, not to mention a well-orchestrated media campaign, Yo has already captured enough attention and users to capitalize on so-called network effects. Once, Twitter was decried as an idea too simplistic to succeed, which might have kept competitors from trying. All the while, it attracted an ever-larger pool of users, which is the real value of any app that aims to connect people and services.
Plus, Yo's team, which now includes 10 part-time and full-time employees, eight of whom are engineers, is actively recruiting outside developers. In various so-called hackathons, they're invited to come up with new uses for the Yo protocol, which is how its bike-sharing and user-authentication applications were thought up.
The more I think about Yo, the more convinced I've become that the only dumb thing about it is the way it sends alerts to a user: as the single word "Yo" in the notifications tray, plus a tinny-sounding voice that says "Yo." At the end of our interview I suggested to Mr. Arbel that he should change "yo" to just about any other word, but he insisted that "yo is the right and only word that can work." When pressed, he concedes that "we are looking into different kinds of Yos."
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