Network effects drive adoption on a single platform as the network value grows according to Metcalfe's law's measure of the number of nodes. The history of fax machine adoption is the clearest example, the first machine was worthless, the second had a little value, the latest one has the greatest.

But I am continue to wonder if Metcalfe's law is an adequate measure of network value when the network is a platform and the network is open. Allow me to provide a recent illustration.

When Feedburner launched its feed splicing service, the initial value proposition was only to publishers by letting them see statistics of their RSS subscriptions. For readers that had already subscribed to a blog with the unspliced feed, there was little incentive to switch.

Now open value added services are being spliced in such as Flickr for photos and Del.icio.us for social bookmarks. With less effort, authors can include new forms of content into their feed that provides. Readers then gain an incentive to switch to the new feed and can do so with nominal switching costs.

The value of the network grows in something closer to Reed's Law of group forming. Flickr and Del.icio.us represent different groups, where what is spliced in is not just the value of the original authors activities, but their participation in the group and options for interactions with others. For example, they can with almost zero effort, copy to amplify a bookmark. Search costs for better bookmarks are reduced because of collective activity in these separate groups.

Participating vendors have combined their applications into a common network platform with nominal transaction costs because of open standards to grow the network as a market as a whole. Certain structural holes persist between applications that are networks. But the incentive to cooperate is accelerating and the marginal value of proprietary protection declines. For example, Skype certainly could remain proprietary after developing a SkypeOut bridge to the traditional telephone network -- that's what carriers do -- and are working on SkypeIn and SkypeWifi. But they have chosen to release an open API. No longer is the circuit circuitous.