(Via Infoworld) Rohit khare writes there are some capabilities that Web-based apps can't handle - yet. Excerpts with edits and comments:
Manuel Kiessling’s open-source ARSC (A Really Simple Chat) uses AJAX techniques to send input lines upstream, whereas a modified HTTP server that holds open thousands of simultaneous connections rebroadcasts the chat stream to other users. The subtler and broader implication of combining AJAX with asynchronous event notification is to extend publish-and-subscribe application integration across the Internet.
The clear benefits of migrating desktop applications to the Web in terms of maintenance, security, and scalability must be weighed against the costs of slower response times, limited interactivity, and less-than-beautiful graphical interfaces. With AJAX, push technology, and the ubiquitous plug-ins for PDF and Flash, the Web is closer than ever to becoming a viable default platform for application development.