I wonder if there is any merit in going a step further and having an annotationMix (or annotationPatch?) (that may or may not be an annotationStream?) that:
1) contains one or more <useAnnotationStream annotationURI="URI-for-annotation-service" /> tags, and
2) defines which bits of those various annotations from each feed should be used in the final annotationMix?
This extension needn't go as far as defining an XSLT to remix the final feed, but would be useful as a config file for a mixer of several feeds, perhaps, or setting up an XSLT to generate the final annotated/mixed feed?
It will be interesting to see what other communities might pick up on RSS annotations, because I have a feeling this idea might run and run....
I'm still working on the specification and hope to get it out soon. The spec needs to be presented with some form of ping service which is going to take a bit more time to set up. I am happy for others to develop ideas based on my original proposal - which I want to keep as simple as possible to allow for maximum exploration of possible application layers.
I'm going to use the tag 'fastreams' to label postings on this topic. It is not ideal, but a check on Technorati for other candidates (fas, annotations) showed that they were taken.