In June I gave a short talk at a conference called Essential Web at the London IMAX. The organizers of the conference had recorded an interview with Tim O’Reilly about the future direction of Web 2.0, and they played back clips of the interview with Tim between the talks.

I was a bit surprised when the clip before my talk rolled. In the video Tim argued in his characteristically soft-spoken but irrefutable way that the mobile phonebook was the killer Web 2.0 application.

In all honesty I wouldn’t have expected the father of Web 2.0 to name the phonebook as the next killer app. Maybe something involving Rails, AJAX, or mashups… but straight off the bat it’s hard to imagine anything more distant from a Web site than the
contact list of a mobile phone.

Today Tim has posted an elaboration of his argument on O’Reilly Radar. As he abandoned his Nokia S60 phone for an iPhone, he found himself missing the presence-enabled phonebook we created for the Nokia handsets. It’s flattering to get acknowledgement for the work the team members at Jaiku – first and foremost our two towering S60 developers Mika Raento and Teemu Kurppa – have been delivering.

Allow me to quote Tim a bit here:

"This is the way a phone address book ought to work. I continue to think that the address book is one of the great untapped Web 2.0 opportunities, and that the phone, even more than email and IM, and
certainly more than an outside-in, invitation-driven "social networking application" represents my real social network. On the series 60 phone, Jaiku was able to embrace and extend the address book. That’s just not possible on the iPhone."

I couldn’t agree more with Tim about the crippling effect the lack of third party applications has on the iPhone. But I worked on a device at Nokia, so I know it isn’t trivial to open up the handset platform to developers. Inevitably, you end up compromising a seamless user experience. Apple, of course, doesn’t like to compromise much there.

Still, I’m optimistic that the iPhone will open up. Apple has all the Web geeks rooting for it. It can’t afford to lose them to a competitor who delivers an equally compelling device with an open platform.

UPDATE:  I elaborated a little on how Apple could open up the iPhone to social web apps in the comments to Tim’s post on O’Reilly Radar