“Every apparently non-polling technology is built on polling”?

Dave Winer is wrong on this one.  He's saying there's no way to do what RSS is doing without polling.
RSS is based on an aggregator connecting to every server that the reader is subscribed to every half hour or so and getting a fresh copy of the RSS feed.  This is wasteful, and it forces the publisher of the content to pay for the bandwith required for people to read it.
Usenet is a different model, but at a lower level (where it's all about the invidual articles posted), it's doing something very similar to what RSS is doing:  Letting a user post something, and letting millions of other users read it.  And it's doing it without polling, and without putting any burden on the person writing the material.
Usenet would be an excellent model for making RSS scaleable.  But hey, NNTP isn't XML-RPC so it's not cool.
Jabber would be another model that would work BTW - a publisher posts a new article and then sends a message, which gets propagated by a network of connected servers to anyone that's interested.  No polling involved at all.