Dave Winer deserves the credit for coming up with the idea long before anyone else. In fact, the element was added to the RSS 2.0 specification in 2001, but has only recently been revived (largely in response to the interest in PuSH). rssCloud made major progress this week with the announcement that WordPress was adding rssCloud support for all 7.5 million blogs on WordPress.com. In contrast, PuSH is currently enabled for well over 100 million feeds with adopters including Friendfeed, Blogger, Google Reader, LiveJournal, Google Alerts and FeedBurner. I expect to see many more services adopt these new protocols soon.