Brandon Duncan, LinkedIn's director of engineering, says LinkedIn members can now search for people's profiles, upload photos, receive network updates and send invitations to connect from their BlackBerrys, iPhones and any other Web-enabled wireless phone that uses the wireless application protocol (WAP).

With the new platform, if a LinkedIn user meets someone at a conference, the user doesn't have to wait until he gets back to his laptop in his hotel room to send an invitation to connect, says Duncan. He can send the invitation to his new contact as she's giving him her e-mail address. "This will allow people to make their networks larger in a shorter period of time," says Duncan, who adds that increasing existing LinkedIn member's usage of the site is a business goal for 2008.

But some existing LinkedIn users with extensive networks expressed doubt about the company's ability to launch the mobile platform successfully at a time when LinkedIn may already be having trouble with its existing functionality.

Bill Howell, senior vice president and CIO of medical components manufacturer Accellent, says he doubts that LinkedIn's infrastructure is capable of keeping up with its 19 million members. "I'm confident that they won't provide support for [the new mobile platform to] those of us who make extensive use of LinkedIn," he says. "They aren't able to support large networks of users on their core infrastructure so I doubt they will be able to do it via a mobile platform."

Howell, who has used LinkedIn since 2004, has 20,000 people in his network and pays $500 for a premium subscription to the service. But he has grown increasingly frustrated with LinkedIn thanks to a laundry list of problems, including an inability to access his inbox, make introductions or conduct simple searches.

When he's contacted LinkedIn's customer service about the problems he's experienced, he says he's been told that his network is too large for the company to handle.

"These limitations in size fly in the face of a cultural storm that is underway with the professional and social networks," he says. "Work gets done via networks of people. My address book was 4,000 entries in 1983. These tools are way behind."