Google's OpenSocial has attracted enormous publicity over the last week - it's seen as the entry of the big beast into social networking, fighting Facebook and Microsoft by transforming the rules of the game.
But I honestly don't think it has changed the rules of the game. The API is only 'open' in the sense that lots of companies have signed up to using it - it does pretty much the same as Facebook's API, albeit using HTML rather than Facebook's weird proprietary markup.
It's the basic premise that I disagree with - that social networks are 'container' applications, within which every other application is hosted, as a 'widget'.
The problem with apps hosted INSIDE social networks is that you get data silos - not everyone I know is in Myspace, and they never will be.
Instead, we need apps that work ACROSS social networks, gathering the relevant friends and details from each to provide the complete picture - e.g. a complete address book.
Writing one of these apps is not about data storage, it's about data aggregation from all across the web. For example, a photo editing website should allow you to import your friends and colleagues from ANY social network, to allow you to collaborate on a picture. That's not possible with OpenSocial.
Of course, I'm sure OpenSocial will be extended in future. Since Brad Fitzpatrick is reportedly behind both OpenID and OpenSocial, I wouldn't be surprised if we see some immediate progress on this front from his employers Google. If my URI for OpenID is the same as my URI for OpenSocial, then whenever I log in someplace, it gets automatic controlled access to my details.
So OpenSocial gets us some of the way there, but the vision is still not complete - it may be a relatively open API, but it currently enforces a closed data model.