Six Apart's announcement about TypeKey is generating some heat - and questions from Dave Winer. By way of a post by Snappy the Clam:

3. Will it be possible for Movable Type and TypePad users to plug into a non-SixApart authentication system?

4. Will the process for designing the API be open or will it be designed exclusively by SixApart? Source

My position on this matter is that centralized user authentication is likely to be run as a business operation, and a service such as TypeKey ultimately helps smaller services compete with agglomerated services such as Yahoo and Google.

It would be ideal for the social software community if SixApart were to create an open, federated system which allows others to maintain alternatives. If they don't, well, we can always work more on an open alternative (there are several out there).