Following this blog post yesterday about my speculation that Google is building a mobile development platform, the whole blogosphere announced this morning that Google is leading an initiative called OpenSocial that will see the launch an open social web API. This new API will allow social networks and application developers to work together using a set of standardized instructions. Partners currently include Google’s Orkut, LinkedIn, Hi5, Friendster, Salesforce.com, Oracle, iLike, Flixster, RockYou, and Slide.

Flickr photo by magerleagues.

As Marc Andreessen said this morning on his blog,

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.

TechCrunch explains in more details:

OpenSocial is a set of three common APIs, defined by Google with input from partners, that allow developers to access core functions and information at social networks:

• Profile Information (user data)
• Friends Information (social graph)
• Activities (things that happen, News Feed type stuff)

Hosts agree to accept the API calls and return appropriate data. Google won’t try to provide universal API coverage for special use cases, instead focusing on the most common uses. Specialized functions/data can be accessed from the hosts directly via their own APIs.

What it means: this is a major announcement, maybe the biggest announcement of the year. Standardizing the social web will go a long way towards the explosion of social as a key element of the Web operating system and one more step towards the web becoming a gigantic word of mouth machine. You’ll want to embrace these standards.

Update: According to AlleyInsider, MySpace will announce today that they join the OpenSocial “alliance”

Update2: Techcrunch reports that blog software publisher SixApart is also joining. Bebo also.