Connecting . . .

Seamus McAteer, an analyst with M:Metrics, said the audience for mobile versions of MySpace and Facebook is growing. But he said, "How many social networks do people really want to belong to, and do they really want another one on their mobile phone?"

The answer, at least for Mig33, is that it offers cheap long-distance calling over the Web in addition to common social-networking features like messaging and photo sharing. By inviting more friends to join the network, Mig33 members can earn credits that they can use to send text messages.

While the firm's name sounds like it has military undertones, Ng said Mig33 simply caught on with users when the service launched in 2005. After gaining a following of about 10 million users overseas -- many of whom are in Asia and South Africa -- the company moved its headquarters from Australia to San Francisco six months ago to tackle the U.S. market. Mig33 counts about 100,000 U.S. users, compared with the millions of mobile MySpace and Facebook memberships.

Made-for-mobile communities like Mig33 may have more revenue opportunities than those that started on the Web, said Christine Perey, who recently wrote a report on social networking for Informa, a market research firm in London. Charging for subscriptions, generating data traffic, and selling things like virtual gifts and video clips have, in some cases, made money for the wireless social networks.

"If it's online, people assume it's going to be free and supported by advertising," she said. By contrast, "people are willing to pay for their mobility and extra features."

But Mig33 isn't the only start-up with that in mind. MocoSpace, based in Boston, lets its 2 million users share photos and videos, chat, and blog from their mobile phones and has received $3 million in funding. In September, Google bought some assets of Zingku, a mobile social network used to exchange invitations, mobile fliers and photos. Groovr, a one-year-old company based in Los Angeles, offers live chats and instant updates about local happenings. Itsmy.com, a two-year-old start-up based in Germany, has built a community by offering free, ad-supported mobile content to members.

Some Mig33 members said it's tough to meet new people on the network, partly because there are so few U.S. users.

Eric Hernandez, 31, of Orlando, said he uses Mig33 to text and call friends in the Netherlands and Africa because it's cheaper than his phone service. But chat-room conversations often turn racy or otherwise inappropriate, so it hasn't opened the door to new friendships, he said.