AIR is an interesting technology merging the web and desktop based applications on the flash platform. Lucas Adamski from Adobe has published a very good article describing the platform and security concerns I'd advise checking out. While it remains to be seen if AIR is going to be the next big thing, the concepts regarding online/offline web applications will be.

Article Link: http://www.adobe.com/devnet/air/articles/introduction_to_air_security.html