Here are some thoughts:

• Write your entire app or site in one consistent paradigm: Ajax.
• Or keep your server-side business logic in Java, PHP, Ruby, etc. and write your presentation layer entirely in Ajax — without exposing your back-end APIs to the web.
• Use the same code or Ajax library to prepare your page on the server and later refresh its contents on the browser.
• Use the same validation logic on the server (for security) and the browser (for interactivity) so they can never get out of sync.
• Access databases, the filesystem, and sockets and protocols (e.g. smtp and xhr) across domains.
• Call server-side JavaScript directly from the browser as if it were client-side — Jaxer makes data wrapping and remote invocation transparent.
• Compensate for limited browsers by running the page on the server and serving the static HTML.
• Overlay Jaxer on top of any other web platform: post-process existing web pages to add functionality without altering their source.

But really, you, the Jaxer community, will come up with the best examples of where Jaxer can be taken!