What are the disadvantages of Ajax?

Following are the disadvantages of Ajax:

    AJAX is dependent on Javascript. If there is some Javascript problem with the browser or in the OS, Ajax will not support
    Ajax can be problematic in Search engines as it uses Javascript for most of its parts.
    Source code written in AJAX is easily human readable. There will be some security issues in Ajax.
     Debugging is difficult
     Increases size of the requests
     Slow and unreliable network connection.
    Problem with browser back button when using AJAX enabled pages.