The combined number users of the initial OpenSocial partners is twice that of Facebook. Since it is an open platform it could easily send the exclusive facebook api to the platform graveyard. Facebook will probably end up jumping on the OpenSocial bandwagon is my guess. Get access to 100 million users. They can use your apps, build your content, and your community.

Not the end of Facebook though because Facebook still has 50 million users. Facebook + OpenSocial = 150 million users.

This is the exact same concept as the Facebook platform, with two huge differences:

With the Facebook platform, only Facebook itself can be a “container” — “apps” can only run within Facebook itself. In contrast, with Open Social, any social network can be an Open Social container and allow Open Social apps to run within it.

With the Facebook platform, app developers build to Facebook-proprietary languages and APIs such as FBML (Facebook Markup Language) and FQL (Facebook Query Language) — those languages and APIs don’t work anywhere other than Facebook — and then the apps can only run within Facebook. In contrast, with Open Social, app developers can build to standard HTML and Javascript, and their apps can then run in any Open Social container.

If you recall how I previously described the Facebook platform as “a dramatic leap forward for the Internet industry”, you’ll understand why I think Open Social is the next big leap forward!

….

Are people really going to maintain multiple sets of front-end pages for their web sites for Facebook, Open Social, etc.?

I think so, yes. I think any web site going forward that wants maximum distribution across the largest number of users will have a single back-end, and then multiple sets of front-end pages:

One set of standard HTML and Javascript pages for consumption by normal web browser.

Another set of HTML and Javascript pages that use the Open Social API’s Javascript calls for consumption with Open Social containers/social networks.

A third set of pages in FBML (Facebook Markup Language) that use Facebook’s proprietary APIs for consumption within Facebook as a Facebook app.

Perhaps a fourth set of pages adapted for the Apple iPhone and/or other mobile devices.