Sean McGrath at ITworld.com - I'll push and you pull. The mashup approach to application integration:

"The mashup phenomenon begs a very pertinent question: can all application integration scenarios that we naturally express in push-centric language, be implemented with pull-centric designs? Is there a limit to what you can do with a mashup - something that would force you to a push-centric approach instead? If every time A needs to send something to B why not get A to publish it, with an RSS/Atom feed instead. Then B can just poll the published information as it sees fit."