AJAX is growing very fast and that is the reason that it contains many issues with it. We hope with the passes of time they will be resolved ab AJAX will be ideal for web applications. We are listing down few issues which AJAX has as a challenge.
Complexity is increased
Server side developers will need to understand that presentation logic will be required in the HTML client pages as well as in the server-side logic
AJAX-based applications can be difficult to debug, test, and maintain
Lack of design patterns or best practice guidelines yet