Jim Winstead has touched an interesting topic in the content distribution world (and specifically in the world of RSS and Atom). In "decentralized web(site|log) update notifications and content distribution" he describes a scenario in which smart aggregation clients do not poll feeds on their own: They instead wait for an update notification from a cloud interface which provides them the fresh data for their local pool. (Oversimplified)
Aside from the unsolved problems like signatures for feeds or privacy, this seems like a rather ideal solution to the problem that feed syndication does not scale terribly well.
In another article on the same topic Jim later asks
how does the publisher know how many people are following what they write?
which is an obvious problem in the clouded world: Due to the fact that most people won't retrieve the full feed anymore, local access logfiles are no measurement for the amount of readership anymore. An approach might be to implement some sort of yet-not-invented stats interface inside the cloud: They should be aware of the number of people that have shown interest in a specific feed and thus they may be able to provide usage statistics to services such as Technorati. (Note that this will only work if all smart aggregation clients sync with the cloud; if they sync between each other, the above technique becomes exceptionally more complicated.)
Sounds like muchos fun.