I've been anxiously awaiting [the iPhone] launch in the hopes that it might show the power of cluster effects wrt mobile phones. Cluster effects describe the emergent practices that occur when the density of infrastructure adoption in a social network reaches a critical tipping point. In other words, cluster effects are the cool things that people do when all of their friends can do the same things. We take cluster effects for granted in the Internet space because, by and large, entire friend groups can jump onto a computer, grab a browser, and login to a website. In terms of clusters, the barriers to Facebook or MySpace are more personal than infrastructural. (Those who lack general access tend to have friends who lack access.) Mobile phones are different. Even if all of my friends have a Nokia N95, the likelihood that we're all on the same carrier with the same plan is next to null. The result is that I can't install an app onto my phone and expect all of my friends to be able to play along. This kills mobile social software from the getgo.
So far, there have been few examples of dense mobile adoption platforms. There's the Crackberry, but that audience isn't exactly the most innovatively social. The Sidekick was impressive amongst deaf communities and urban youth, but T-Mobile managed to lock that puppy down so heavily that no innovative practices really emerged. Still, if you look at the AIM usage in those clusters, you get a good indicator of the potential. And that's all folks.
The iPhone has the best chance of hitting that tipping point of anything out there. For the most part, everyone is stuck on AT&T. And everyone gets a data plan. And the phone is semi-open. The price is still out of reach for most high schoolers who rely on parental pass-me-downs, but it has a decent chance of hitting other clusters. I was banking on urban 20-somethings, but I love the idea of it hitting cab driver clusters.