Jeff's recent post about the Birds of a Feather session at this year's OSCON to add a bunch of R content got me thinking along these lines. It might be nice to have a way of identifying which questions and answers were entered during certain events or by user groups. This could make organizing the groups easier.
Some of this could be accomplished by tagging but it seems like that would be bad form since the tag wouldn't directly relate to the content of the Q/A, but rather to the poster or event. I wonder if a group or guild system would be abused.
I also wonder if this is something that would necessarily need to be part of StackOverflow core. If the platform has a good web service API a group system could be developed by a 3rd party.