I read this article [Unobtrusive JavaScript with jQuery][1]
and I noticed these points in the slide page **11**

 - some companies strip JavaScript at the firewall
 - some run the NoScript Firefox extension to protect themselves from common XSS and CSRF attacks
 - many mobile devices ignore JavaScript entirely
 - screen readers **do** execute JavaScript but accessibility issues mean you may not want them to


I did not understand the fourth point. What does it mean?

I need your comment and responses on these points. Is not using JavaScript and switching to libraries like jQuery worth it?

 [1]: http://simonwillison.net/static/2008/xtech/