The Internet already swirls with millions of images created by consumers using digital cameras. And by the end of 2004, some 180 million cell phones worldwide will have cameras built in, according to InfoTrends/CAP Ventures, an analysis firm in Weymouth, MA. So it’s not surprising that one of the fastest-growing Internet applications is online photo sharing: the creation of individual or group Web albums where people can upload digital snapshots and invite friends to view and comment on them or order prints.

Not only is it becoming one of the hottest uses of the Web, but it’s also driving a booming business in the sale of website memberships and photo prints. Compared to overall e-commerce revenues, which reached some $54.9 billion last year, earnings at commercial photo-sharing sites in North America are still small, totaling $124 million in the same period; but they’re set to increase to $206 million this year, says Jill Aldort, a senior research analyst at InfoTrends. And several companies, including Microsoft, are introducing technologies intended to turn photo sharing into the basis for supercharged social-computing experiences, meaning everything from photo-enhanced instant messaging to community organizing and networking.

Commercial photo-sharing websites where users can create online photo albums and order prints have been around almost as long as the Web; the names most familiar to consumers today are Ofoto, Shutterfly, Snapfish, and PhotoWorks. A few years ago, Internet users invented a more community-based alternative, the photo weblog. One example is Fotolog.net-a popular “photoblog” that has accumulated some 345,000 members since its founding in 2002. Basic membership is free, but a $5-a-month subscription allows members to upload more photos per day, and during peak hours. “Nowadays people are carrying around cameras in their pockets and briefcases and purses,” says CEO Adam Seifer. “They’re going, Look at that graffiti or that shadow on the wall,’ or That’s the craziest dog I’ve ever seen,’ or That sign is misspelled.’ What do they do with these photos? There were tools like Ofoto and Shutterfly for reprints, but those aren’t as satisfying as an interactive experience with other human beings. When people participate in [Fotolog], they become part of something bigger than just themselves.”

But Fotolog’s content is static: users must check in periodically to see what others have said about their photos. At Vancouver, British Columbia-based Ludicorp, programmers have made it easy to share photos during real-time conversations. Flickr.com, launched by Ludicorp in February, lets users upload photos to personal “shoeboxes,” set up group instant-messaging conferences with their friends, tag all or parts of a photo with personal notes, and intersperse their text-based conversations with images simply by dragging photos from their shoeboxes to the messaging window. As with Fotolog, basic membership in Flickr is free, but the company plans to introduce subscription-only “pro” accounts offering more storage.

And now, in perhaps the ultimate confirmation that photo sharing is a hot trend, the world’s largest software company is getting into the act. At Microsoft Research in Redmond, WA, researchers in the company’s social-computing group are working on a program code-named Wallop. It offers most of the features of Fotolog and Flickr but takes the idea of photo-as-conversation-starter several steps further.

For example, when a user adds a personal note to a photo-say, a wry comment on a photo of a tipsy coworker at the company picnic-a notice about the comment is automatically e-mailed to the people on the user’s friends list or to an extended network of contacts. The program follows the ensuing thread of e-mail conversation and lets users display graphical depictions of their social networks so they can see who’s online and who has added comments recently. Wallop members will eventually be able to share music files and videos as well, says Sean Kelly, a software developer in the Microsoft group.

About 150 volunteers are trying the software, including a group of Puget Sound paragliders who use the service to share and discuss photos of their latest outings. If the researchers can figure out how to support thousands of simultaneous users, a much larger trial may get under way later this year. But despite all the programming work going into Wallop, it “isn’t necessarily a technology project at all,” says Kelly. “It’s more about how these groups of friends are evolving and what kind of technology they are going to need in the future, and how the Web and multimedia can all play a part.”

It’s unclear how soon Wallop, or parts of it, might be folded into fully supported Microsoft products such as MSN. But whatever the timetable, Wallop represents one of Microsoft’s biggest precommercial forays into social computing. “I would think that any type of photo-sharing program that they introduce-particularly if it’s part of Windows or MSN-is going to be successful,” says InfoTrends’ Aldort.

At bottom, projects like Wallop and Flickr are a response to the emergence of a generation of people for whom computing is primarily a way to create and strengthen social ties. In Japan, the United States, and Canada, for example, gadget-crazy consumers are using their cell phones, laptops, digital cameras, camera phones, and wireless Internet connections to keep in near-constant touch with their friends and colleagues. “There’s a sense that you are carrying your social relations around with you in your pocket,” says Mizuko Ito, a University of Southern California anthropologist who studies cell-phone use in Japan. Photo-sharing sites are becoming both an archive and a launching point for such interactions. And for Internet users-not to mention software and device makers-that adds up to a very pretty picture.