GME allowed application feeds to be shared. But now due to changes made to the GME, user feeds which were private previously, are now shareable. Now this might bring out more mashable ideas!
Feedotopia is currently playing with GME in certain features and hope to use this new opening to the fullest as our application is completely user based.
If you want to see examples of this feature, have a look at MultiTask (a shared task list) and My Travel Map, ( a travelling mashup?).
Feeds are shareable