Facebook made oversharing with a small army of friends a mainstream activity. Now, one of its early architects is swinging in the other direction.

Dave Morin, who helped build Facebook Connect and the Facebook Platform, left the company this year to start his own venture, called Path. He says it is not another social network he has created, but a personal network, and on Monday, it will open to the public with an iPhone app for sharing cellphone photos with a limited circle of friends.
Each user cannot have more than 50 friends.
Path is a reaction to Facebook, where people must both agree to be friends, but can have thousands of them, and Twitter, where anyone can choose to receive a user’s posts.
“If you look at how these networks are grown, they start out really high-quality,” said Mr. Morin, “and as more and more people join, it becomes hard to find people you care about. With Path, you have to be friends with them in the real world in order for them to pop up on your screen.”
Path, which is starting with the iPhone app and a Web site and plans to build apps for Android and BlackBerry, has kept its plans shrouded in secrecy. It now joins a growing list of similar apps, like Instagram and PicPlz. The apps are part of several big trends. As cellphone cameras have improved, people are taking more photos than ever before. Tech entrepreneurs and investors are betting that these photographers also want to share their handiwork, especially in real-time and linked to their location.

Path, along with the other apps, wants to build a broader mobile network, not just photo-sharing apps. It envisions people using a new mobile social network, in addition to Facebook, to share photos, videos and other things with a close-knit group. However, the rival apps differ from Path by offering software filters, which change the way photos look. They also follow Twitter’s model, so any user can see anyone else’s pictures.
Path is counting on people wanting a more controlled network of trusted friends. Mr. Morin chose the number 50 based on the research of Robin Dunbar, an anthropologist who tried to pinpoint the maximum number of people with whom others could have stable relationships. The Dunbar number, generally thought to be around 150, is a popular topic of discussion in Silicon Valley among people building tools to communicate virtually with thousands of people.

But Mr. Morin is focused on a different one of Mr. Dunbar’s numbers — the number of people that an individual knows and trusts, like the group you would invite to a birthday party. That number is between 40 and 60, Mr. Morin said.
Though Facebook allows users to limit their friends or create private groups, Facebook abstainers “simply don’t feel like they have a private enough place to share,” Mr. Morin said. “The devil’s in the defaults,” he said, and Path’s default will be to limit sharing.

On Path, people tag photos with the names of people, places and things. At its makeshift office in an apartment on the 40th floor of a glass high-rise overlooking San Francisco Bay, people have tagged mocha, fireworks, foie gras, selling emotion and beer.
The tags stay in the database for others to use, which has given birth to memes, like one in the Path office for Happy Socks, a brand of patterned socks that are a favorite of Mr. Morin and Matt Van Horn, Path’s vice president of business.
Users can pick up to 50 friends to see their photos. The friendship does not have to be mutual, so they might send photos to someone who does not send photos to them. With one swipe, users can also make a picture visible only to the people tagged in it, so friends who were not invited to a dinner party won’t feel left out, for instance.
“We solve for that social ambiguity that we all have in the real world,” Mr. Morin said.
Academics who research the way we socialize online say that social networks that group all our friends, colleagues and acquaintances together do not accurately reflect our offline relationships, which can be a source of tension for Internet users.
“People are not able to see that this technology can offer them the same level of protection and behavior patterns that they are used to in their offline lives, so they feel violated,” said S. Shyam Sundar, co-director of the Media Effects Research Laboratory at Pennsylvania State University who is currently a visiting professor in South Korea.
But people already using Facebook — and LinkedIn, Ping, Foursquare, Google Buzz or others — may have a severe case of social-networking fatigue when asked to join yet another service.
“There were a whole slew of mobile-only social networks that you never heard of that were all trying to beat Facebook for this new medium,” said Greg Sterling, an analyst who researches the mobile Internet. “They either got bought or just shriveled up.”
Chris Kelly, Facebook’s former chief privacy officer, contributed to Path’s $2.5 million in angel investment. “I think everyone’s going to have a Facebook account and use it for broader distribution, but I also think they’re going to have a very tightly controlled set of friends they share deeply connected moments with,” he said. “I think that Path could be the network for that.”
Path has not yet figured out how it will make money, though it says it has considered selling services like filters or themes for photographs or advertising. The limited number of people could make it difficult to attract advertisers, but Mr. Morin thinks otherwise:
“Because people are posting such immense amounts of information about their lives, there could be more opportunities for brands to talk to Path users in a more personal way than they ever have before.”

By CLAIRE CAIN MILLER (NYT),November 15, 2010