What the heck is MEF:
MEF is a set of features referred in the academic community and in the industry as a Naming and Activation Service (returns an object given a “name”), Dependency Injection (DI) framework, and a Structural Type System (duck typing). These technologies (and other like System.AddIn) together are intended to enable the world of what we call Open and Dynamic Applications, i.e. make it easier and cheaper to build extensible applications and extensions.
Cool, and it gets cooler:
The direct engagement with the DI community is also starting. We gave a talk on the technology at last week’s MVP Summit, and talked with Jeremy Miller (the owner of Structure Map) and Ayende Rahien (Rhino Mocks)
There's a trend of openness at Microsoft that you could never predict a few years ago. Good job!