In his post Really Simple Sharing, Ray Ozzie announced Simple Sharing Extensions for RSS and OPML. He writes

As an industry, we have simply not designed our calendaring and directory software and services for this “mesh” model. The websites, services and servers we build seem to all want to be the “owner” and “publisher”; it’s really inconsistent with the model that made email so successful, and the loosely-coupled nature of the web.

Shortly after I started at Microsoft, I had the opportunity to meet with the people behind Exchange, Outlook, MSN, Windows Mobile, Messenger, Communicator, and more. We brainstormed about this “meshed world” and how we might best serve it - a world where each of these products and others’ products could both manage these objects and synchronize each others’ changes. We thought about how we might prototype such a thing as rapidly as possible – to get the underpinnings of data synchronization working so that we could spend time working on the user experience aspects of the problem – a much better place to spend time than doing plumbing.

There are many great item synchronization mechanisms out there (and at Microsoft), but we decided we’d never get short term network effects among products if we selected something complicated – even if it were powerful. What we really longed for was "the RSS of synchronization" ... something simple that would catch on very quickly.

Using RSS itself as-is for synchronization wasn't really an option. That is, RSS is primarily about syndication - unidirectional publishing - while in order to accomplish the “mesh” sharing scenarios, we'd need bi-directional (actually, multi-directional) synchronization of items. But RSS is compelling because of the power inherent in its simplicity.
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And so we created an RSS extension that we refer to as Simple Sharing Extensions or SSE. In just a few weeks time, several Microsoft product groups and my own 'concept development group' built prototypes and demos, and found that it works and interoperates quite nicely.

We’re pretty excited about the extension - well beyond the uses that catalyzed its creation. It’s designed in such a way that the minimum implementation is incredibly easy, and so that higher-level capabilities such as conflict handling can be implemented in those applications that want to do such things.

The model behind SSE is pretty straightforward; to sychronize data across multiple sources, each end point provides a feed and the subscribes to the feeds provided by the other end point(s).  I hate to sound like a fanboy but SSE is an example of how Ray Ozzie showed up at Microsoft and just started kicking butt. I've been on the periphery of some of the discussions of SSE and reviewed early drafts of the spec. It's been impressive seeing how much quick progress Ray made internally on getting this idea polished and evangelized.

The spec looks good modulo the issues that tend to dog Microsoft when it ships specs like this. For example,  is a lack of detail around data types (e.g. nowhere is the date format used by the spec documented although you can assume it's RFC 822 dates based on the examples) and there is also the lack of any test sites that have feeds which use this format so enterprising hackers can quickly write some code to prototype implementations and try out ideas.

Sam Ruby has posted a blog entry critical of Microsoft's practices when it publishes RSS extension specifications in his post This is Sharing? where he writes

The first attribute that the the Simple Sharing Extensions for RSS and OPML is to “treat the item list as an ordered set”.  This sounds like something from the Simple List Extensions Specification that was also hatched in private and then unleashed with great fanfare about five months ago. Sure a wiki was set up, but any questions posted there were promptly ignored.  The cone of silence has been so impenetrable that even invoking the name Scoble turns out to be ineffective. 

Now the Simple List Extensions Specification URI redirects to an ad for vaporware.  Some things never change.

Should we wait for version 3.0?

I agree with all of Sam's feedback. Hopefully Microsoft will do better this time around.