Likely referring to web-apps that require Javascript support and have no fail over code. This is more a problem with the developer of said site and not an issu

Likely referring to web-apps that require Javascript support and have no fail over code. This is more a problem with the developer of said site and not an issue with XMLhttprequest as you can build apps that are progressively enhanced for it and don't fail completely when JS/XMLHTTP is disabled.